Custodian Account UI: CRUD (#3923)

* WIP New APIs for dealing with custodians/exchanges

* Simplified things

* More API refinements + index.html file for quick viewing

* Finishing touches on spec

* Switched cryptoCode to paymentMethod as this allows us to differentiate between onchain and lightning

* Moved draft API docs to "/docs-draft"

* WIP baby steps

* Added DB migration for CustodianAccountData

* Rough but working POST /v1/api/custodian-account + GET /v1/api/custodian

* WIP + early Kraken API client

* Moved service registration to proper location

* Working create + list custodian accounts + permissions + WIP Kraken client

* Kraken API Balances call is working

* Added asset balances to response

* List Custodian Accounts call does not load assetBalances by default, because it can fail. Can be requested when needed.

* Call to get the details of 1 specific custodian account

* Added permissions to swagger

* Added "tradableAssetPairs" to Kraken custodian response + cache the tradable pairs in memory for 24 hours

* Removed unused file

* WIP + Moved files to better locations

* Updated docs

* Working API endpoint to get info on a trade (same response as creating a new trade)

* Working API endpoints for Deposit + Trade + untested Withdraw

* Delete custodian account

* Trading works, better error handling, cleanup

* Working withdrawals + New endpoint for getting bid/ask prices

* Completed withdrawals + new endpoint for getting info on a past withdrawal to simplify testing, Enums are output as strings,

* Better error handling when withdrawing to a wrong destination

* WithdrawalAddressName in config is now a string per currency (dictionary)

* Added TODOs

* Only show the custodian account "config" to users who are allowed

* Added the new permissions to the API Keys UI

* Renamed KrakenClient to KrakenExchange

* WIP Kraken Config Form

* Removed files for UI again, will make separate PR later

* Fixed docs + Refactored to use PaymentMethod more + Added "name" to custodian account + Using cancelationToken everywhere

* Updated withdrawal info docs

* First unit test

* Complete tests for /api/v1/custodians and /api/v1/custodian-accounts endpoints + Various improvements and fixes

* Mock custodian and more exceptions

* Many more tests + cleanup, moved files to better locations

* More tests

* WIP more tests

* Greenfield API tests complete

* Added missing "Name" column

* Cleanup, TODOs and beginning of Kraken Tests

* Added Kraken tests using public endpoints + handling of "SATS" currency

* Added 1st mocked Kraken API call: GetAssetBalancesAsync

* Added assert for bad config

* Mocked more Kraken API responses + added CreationDate to withdrawal response

* pr review club changes

* Make Kraken Custodian a plugin

* Re-added User-Agent header as it is required

* Fixed bug in market trade on Kraken using a percentage as qty

* A short delay so Kraken has the time to execute the market order and we don't fetch the details too quickly.

* Merged the draft swagger into the main swagger since it didn't work anymore

* Fixed API permissions test

* Removed 2 TODOs

* Fixed unit test

* After a utxo rescan, the cached balance should be invalidated

* Fixed Kraken plugin build issues

* Added Kraken plugin to build

* WIP UI + config form

* Create custodian account almost working - only need to add in the config form

* Working form, but lacks refinement

* Viewing balances + Editing custodian account works, but cannot change the withdrawal destination config because that is an object using a name with [] in it

* cleanup

* Minor cleanup, comments

* Working: Delete custodian account

* Moved the MockCustodian used in tests to a new plugin + linked it to the tests

* WIP viewing custodian account balances

* Split the Mock custodian into a Mock + Fake, various UI improvements and minor fixes

* Minor UI fixes

* Removed broken link

* Removed links to anchors as they cannot pass the tests since they use JavaScript

* Removed non-existing link. Even though it was commented out, the test still broke?

* Added TODOs

* Now throwing BadConfigException if API key is invalid

* UI improvements

* Commented out unfinished API endpoints. Can be finished later.

* Show fiat value for fiat assets

* Removed Kraken plugin so I can make a PR


Removed more Kraken files

* Add experimental route on UICustodianAccountsControllre

* Removed unneeded code

* Cleanup code

* Processed Nicolas' feedback

Co-authored-by: Kukks <evilkukka@gmail.com>
Co-authored-by: nicolas.dorier <nicolas.dorier@gmail.com>

BTCPayServer.Abstractions/Custodians/ICustodian.cs

@@ -1,6 +1,7 @@
 using System.Collections.Generic;
 using System.Threading;
 using System.Threading.Tasks;
+using BTCPayServer.Client.Models;
 using Newtonsoft.Json.Linq;
 
 namespace BTCPayServer.Abstractions.Custodians;
@@ -18,4 +19,8 @@ public interface ICustodian
      * Get a list of assets and their qty in custody.
      */
     Task<Dictionary<string, decimal>> GetAssetBalancesAsync(JObject config, CancellationToken cancellationToken);
+
+    public Task<Form.Form> GetConfigForm(JObject config, string locale,
+        CancellationToken cancellationToken = default);
+
 }

BTCPayServer.Abstractions/Extensions/CustodianExtensions.cs

@@ -0,0 +1,14 @@
+#nullable enable
+using System.Collections.Generic;
+using System.Linq;
+using BTCPayServer.Abstractions.Custodians;
+
+namespace BTCPayServer.Abstractions.Extensions;
+
+public static class CustodianExtensions
+{
+    public static ICustodian? GetCustodianByCode(this IEnumerable<ICustodian> custodians, string code)
+    {
+        return custodians.FirstOrDefault(custodian => custodian.Code == code);
+    }
+}

BTCPayServer.Abstractions/Form/AlertMessage.cs

@@ -0,0 +1,37 @@
+using Newtonsoft.Json;
+using Newtonsoft.Json.Converters;
+
+namespace BTCPayServer.Abstractions.Form;
+
+public class AlertMessage
+{
+    // Corresponds to the Bootstrap CSS "alert alert-xxx" messages:
+    // Success = green
+    // Warning = orange
+    // Danger = red
+    // Info = blue
+    public enum AlertMessageType
+    {
+        Success,
+        Warning,
+        Danger,
+        Info
+    }
+    
+    [JsonConverter(typeof(StringEnumConverter))]
+    public AlertMessageType Type;
+    
+    // The translated message to be shown to the user
+    public string Message;
+
+    public AlertMessage()
+    {
+        
+    }
+
+    public AlertMessage(AlertMessageType type, string message)
+    {
+        this.Type = type;
+        this.Message = message;
+    }
+}

BTCPayServer.Abstractions/Form/Field.cs

@@ -0,0 +1,35 @@
+using System.Collections.Generic;
+
+namespace BTCPayServer.Abstractions.Form;
+
+public abstract class Field
+{
+    // HTML5 compatible type string like "text", "textarea", "email", "password", etc. Each type is a class and may contain more fields (i.e. "select" would have options).
+    public string Type;
+    
+    // The name of the HTML5 node. Should be used as the key for the posted data.
+    public string Name;
+    
+    // The translated label of the field.
+    public string Label;
+    
+    // The value field is what is currently in the DB or what the user entered, but possibly not saved yet due to validation errors.
+    // If this is the first the user sees the form, then value and original value are the same. Value changes as the user starts interacting with the form.
+    public string Value;
+
+    // The original value is the value that is currently saved in the backend. A "reset" button can be used to revert back to this. Should only be set from the constructor.
+    public string OriginalValue;
+
+    // A useful note shown below the field or via a tooltip / info icon. Should be translated for the user.
+    public string HelpText;
+    
+    // The field is considered "valid" if there are no validation errors
+    public List<string> ValidationErrors = new List<string>();
+
+    public bool Required = false;
+
+    public bool IsValid()
+    {
+        return ValidationErrors.Count == 0;
+    }
+}

BTCPayServer.Abstractions/Form/Fieldset.cs

@@ -0,0 +1,14 @@
+using System.Collections.Generic;
+
+namespace BTCPayServer.Abstractions.Form;
+
+public class Fieldset
+{
+    public Fieldset()
+    {
+        this.Fields = new List<Field>();
+    }
+
+    public string Label { get; set; }
+    public List<Field> Fields { get; set; }
+}

BTCPayServer.Abstractions/Form/Form.cs

@@ -0,0 +1,60 @@
+using System.Collections.Generic;
+
+namespace BTCPayServer.Abstractions.Form;
+
+public class Form
+{
+
+    // Messages to be shown at the top of the form indicating user feedback like "Saved successfully" or "Please change X because of Y." or a warning, etc...
+    public List<AlertMessage> TopMessages { get; set; } = new();
+    
+    // Groups of fields in the form
+    public List<Fieldset> Fieldsets { get; set; } = new();
+    
+
+    // Are all the fields valid in the form?
+    public bool IsValid()
+    {
+        foreach (var fieldset in Fieldsets)
+        {
+            foreach (var field in fieldset.Fields)
+            {
+                if (!field.IsValid())
+                {
+                    return false;
+                }
+            }
+        }
+
+        return true;
+    }
+
+    public Field GetFieldByName(string name)
+    {
+        foreach (var fieldset in Fieldsets)
+        {
+            foreach (var field in fieldset.Fields)
+            {
+                if (name.Equals(field.Name))
+                {
+                    return field;
+                }
+            }
+        }
+        return null;
+    }
+
+    public List<string> GetAllNames()
+    {
+        var names = new List<string>();
+        foreach (var fieldset in Fieldsets)
+        {
+            foreach (var field in fieldset.Fields)
+            {
+                names.Add(field.Name);
+            }
+        }
+
+        return names;
+    }
+}

BTCPayServer.Abstractions/Form/TextField.cs

@@ -0,0 +1,19 @@
+namespace BTCPayServer.Abstractions.Form;
+
+public class TextField : Field
+{
+    public TextField(string label, string name, string value, bool required, string helpText)
+    {
+        this.Label = label;
+        this.Name = name;
+        this.Value = value;
+        this.OriginalValue = value;
+        this.Required = required;
+        this.HelpText = helpText;
+        this.Type = "text";
+    }
+
+    // TODO JSON parsing from string to objects again probably won't work out of the box because of the different field types. 
+    
+
+}

BTCPayServer.Data/Data/CustodianAccountData.cs

@@ -19,6 +19,7 @@ public class CustodianAccountData
     [MaxLength(50)]
     public string CustodianCode { get; set; }
     
+    [Required]
     [MaxLength(50)]
     public string Name { get; set; }
     

BTCPayServer.Tests/GreenfieldAPITests.cs

@@ -1,28 +1,23 @@
 using System;
 using System.Collections.Generic;
 using System.Globalization;
-using System.IO;
 using System.Linq;
 using System.Net.Http;
 using System.Threading;
 using System.Threading.Tasks;
 using BTCPayServer.Abstractions.Contracts;
 using BTCPayServer.Abstractions.Custodians;
-using BTCPayServer.Abstractions.Extensions;
 using BTCPayServer.Client;
 using BTCPayServer.Client.Models;
 using BTCPayServer.Controllers;
 using BTCPayServer.Events;
-using BTCPayServer.JsonConverters;
 using BTCPayServer.Lightning;
 using BTCPayServer.Models.InvoicingModels;
 using BTCPayServer.Payments;
-using BTCPayServer.Services;
-using BTCPayServer.Services.Custodian.Client;
 using BTCPayServer.Services.Custodian.Client.MockCustodian;
+using BTCPayServer.Services;
 using BTCPayServer.Services.Notifications;
 using BTCPayServer.Services.Notifications.Blobs;
-using BTCPayServer.Tests.Logging;
 using Microsoft.AspNetCore.Mvc;
 using Microsoft.EntityFrameworkCore;
 using NBitcoin;
@@ -31,9 +26,7 @@ using Newtonsoft.Json;
 using Newtonsoft.Json.Linq;
 using Xunit;
 using Xunit.Abstractions;
-using Xunit.Sdk;
 using CreateApplicationUserRequest = BTCPayServer.Client.Models.CreateApplicationUserRequest;
-using JsonReader = Newtonsoft.Json.JsonReader;
 
 namespace BTCPayServer.Tests
 {
@@ -2586,7 +2579,7 @@ namespace BTCPayServer.Tests
             var clientBasic = await user.CreateClient();
             var custodians = await clientBasic.GetCustodians();
             Assert.NotNull(custodians);
-            Assert.Single(custodians);
+            Assert.NotEmpty(custodians);
         }
 
 
@@ -2680,13 +2673,23 @@ namespace BTCPayServer.Tests
             Assert.Single(viewerCustodianAccounts);
             Assert.Equal(viewerCustodianAccounts.First().CustodianCode, custodian.Code);
             Assert.Null(viewerCustodianAccounts.First().Config);
+            
+            // Wrong store ID
+            await AssertApiError(403, "missing-permission", async () => await adminClient.GetCustodianAccounts("WRONG-STORE-ID"));
+            
 
             
-            // Try to fetch 1
+            // Try to fetch 1 custodian account
             // Admin
             var singleAdminCustodianAccount = await adminClient.GetCustodianAccount(storeId, accountId);
             Assert.NotNull(singleAdminCustodianAccount);
             Assert.Equal(singleAdminCustodianAccount.CustodianCode, custodian.Code);
+            
+            // Wrong store ID
+            await AssertApiError(403, "missing-permission",async () => await adminClient.GetCustodianAccount("WRONG-STORE-ID", accountId));
+            
+            // Wrong account ID
+            await AssertApiError(404, "custodian-account-not-found",async () => await adminClient.GetCustodianAccount(storeId, "WRONG-ACCOUNT-ID"));
 
             // Manager can see, including config
             var singleManagerCustodianAccount = await managerClient.GetCustodianAccount(storeId, accountId);
@@ -2789,8 +2792,6 @@ namespace BTCPayServer.Tests
             // Load a custodian, we use the first one we find.
             var custodians  = tester.PayTester.GetService<IEnumerable<ICustodian>>();
             var mockCustodian = custodians.First(c => c.Code == "mock");
-
-            
             
              // Create custodian account
              var createCustodianAccountRequest = new CreateCustodianAccountRequest();

BTCPayServer.Tests/MockCustodian/MockCustodian.cs

@@ -3,6 +3,7 @@ using System.Collections.Generic;
 using System.Threading;
 using System.Threading.Tasks;
 using BTCPayServer.Abstractions.Custodians;
+using BTCPayServer.Abstractions.Form;
 using BTCPayServer.Client.Models;
 using Newtonsoft.Json.Linq;
 
@@ -50,6 +51,11 @@ public class MockCustodian : ICustodian, ICanDeposit, ICanTrade, ICanWithdraw
         return Task.FromResult(r);
     }
 
+    public Task<Form> GetConfigForm(JObject config, string locale, CancellationToken cancellationToken = default)
+    {
+        return null;
+    }
+
     public Task<DepositAddressData> GetDepositAddressAsync(string paymentMethod, JObject config, CancellationToken cancellationToken)
     {
         if (paymentMethod.Equals(DepositPaymentMethod))

BTCPayServer/BTCPayServer.csproj

@@ -147,6 +147,7 @@
 	  <ProjectReference Include="..\BTCPayServer.Data\BTCPayServer.Data.csproj" />
 	  <ProjectReference Include="..\BTCPayServer.Rating\BTCPayServer.Rating.csproj" />
 	  <ProjectReference Include="..\BTCPayServer.Common\BTCPayServer.Common.csproj" />
+	  <ProjectReference Include="..\Plugins\BTCPayServer.Plugins.Custodians.FakeCustodian\BTCPayServer.Plugins.Custodians.FakeCustodian.csproj" />
 	</ItemGroup>
 
 	<ItemGroup>

BTCPayServer/Components/MainNav/Default.cshtml

@@ -8,7 +8,14 @@
 @using BTCPayServer.Abstractions.Extensions
 @using BTCPayServer.Abstractions.Contracts
 @using BTCPayServer.Client
+@using BTCPayServer.Components.Icon
+@using BTCPayServer.Components.ThemeSwitch
+@using BTCPayServer.Components.UIExtensionPoint
+@using BTCPayServer.Security
 @using BTCPayServer.Services
+@using BTCPayServer.TagHelpers
+@using BTCPayServer.Views.CustodianAccounts
+@using Microsoft.AspNetCore.Mvc.TagHelpers
 @inject BTCPayServer.Services.BTCPayServerEnvironment Env
 @inject SignInManager<ApplicationUser> SignInManager
 @inject PoliciesSettings PoliciesSettings
@@ -92,6 +99,30 @@
                                         
                                     </li>
                                 }
+                                
+                                @if (PoliciesSettings.Experimental)
+                                {
+                                    @foreach (var custodianAccount in Model.CustodianAccounts)
+                                    {
+                                        <li class="nav-item">
+                                            <a asp-area="" asp-controller="UICustodianAccounts" asp-action="ViewCustodianAccount" asp-route-storeId="@custodianAccount.StoreId" asp-route-accountId="@custodianAccount.Id" class="nav-link js-scroll-trigger @ViewData.IsActivePage(CustodianAccountsNavPages.View, custodianAccount.Id)" id="@($"StoreNav-CustodianAccount-{custodianAccount.Id}")">
+                                                <!--
+                                                TODO which icon should we use?
+                                                -->
+                                                <span>@custodianAccount.Name</span>
+                                                <span class="badge bg-warning ms-1" style="font-size:10px;">Experimental</span>
+                                            </a>
+                                        </li>
+                                    }
+                                    <li class="nav-item">
+                                        <a asp-area="" asp-controller="UICustodianAccounts" asp-action="CreateCustodianAccount" asp-route-storeId="@Model.Store.Id" class="nav-link js-scroll-trigger @ViewData.IsActivePage(CustodianAccountsNavPages.Create)" id="StoreNav-CreateApp">
+                                            <vc:icon symbol="new"/>
+                                            <span>Add Custodian</span>
+                                            <span class="badge bg-warning ms-1" style="font-size:10px;">Experimental</span>
+                                        </a>
+                                    </li>
+                                }
+                                
                             </ul>
                         </div>
                     </div>

BTCPayServer/Components/MainNav/MainNav.cs

@@ -6,7 +6,9 @@ using BTCPayServer.Data;
 using BTCPayServer.Models.StoreViewModels;
 using BTCPayServer.Payments;
 using BTCPayServer.Payments.Lightning;
+using BTCPayServer.Services;
 using BTCPayServer.Services.Apps;
+using BTCPayServer.Services.Custodian.Client;
 using BTCPayServer.Services.Invoices;
 using BTCPayServer.Services.Stores;
 using Microsoft.AspNetCore.Identity;
@@ -25,6 +27,7 @@ namespace BTCPayServer.Components.MainNav
         private readonly BTCPayNetworkProvider _networkProvider;
         private readonly UserManager<ApplicationUser> _userManager;
         private readonly PaymentMethodHandlerDictionary _paymentMethodHandlerDictionary;
+        private readonly CustodianAccountRepository _custodianAccountRepository;
 
         public MainNav(
             AppService appService,
@@ -32,7 +35,9 @@ namespace BTCPayServer.Components.MainNav
             UIStoresController storesController,
             BTCPayNetworkProvider networkProvider,
             UserManager<ApplicationUser> userManager,
-            PaymentMethodHandlerDictionary paymentMethodHandlerDictionary)
+            PaymentMethodHandlerDictionary paymentMethodHandlerDictionary,
+            CustodianAccountRepository custodianAccountRepository,
+            PoliciesSettings policiesSettings)
         {
             _storeRepo = storeRepo;
             _appService = appService;
@@ -40,6 +45,8 @@ namespace BTCPayServer.Components.MainNav
             _networkProvider = networkProvider;
             _storesController = storesController;
             _paymentMethodHandlerDictionary = paymentMethodHandlerDictionary;
+            _custodianAccountRepository = custodianAccountRepository;
+            PoliciesSettings = policiesSettings;
         }
 
         public async Task<IViewComponentResult> InvokeAsync()
@@ -68,11 +75,21 @@ namespace BTCPayServer.Components.MainNav
                     AppType = a.AppType,
                     IsOwner = a.IsOwner
                 }).ToList();
+
+
+                if (PoliciesSettings.Experimental)
+                {
+                    // Custodian Accounts
+                    var custodianAccounts = await _custodianAccountRepository.FindByStoreId(store.Id);
+                    vm.CustodianAccounts = custodianAccounts;
+                }
             }
 
             return View(vm);
         }
 
         private string UserId => _userManager.GetUserId(HttpContext.User);
+
+        public PoliciesSettings PoliciesSettings { get; }
     }
 }

BTCPayServer/Components/MainNav/MainNavViewModel.cs

@@ -10,6 +10,7 @@ namespace BTCPayServer.Components.MainNav
         public List<StoreDerivationScheme> DerivationSchemes { get; set; }
         public List<StoreLightningNode> LightningNodes { get; set; }
         public List<StoreApp> Apps { get; set; }
+        public CustodianAccountData[] CustodianAccounts { get; set; }
         public bool AltcoinsBuild { get; set; }
     }
 

BTCPayServer/Controllers/GreenField/GreenfieldCustodianAccountController.cs

@@ -7,6 +7,7 @@ using System.Threading.Tasks;
 using BTCPayServer.Abstractions.Constants;
 using BTCPayServer.Abstractions.Custodians;
 using BTCPayServer.Abstractions.Extensions;
+using BTCPayServer.Abstractions.Form;
 using BTCPayServer.Client;
 using BTCPayServer.Client.Models;
 using BTCPayServer.Data;
@@ -18,6 +19,7 @@ using Microsoft.AspNetCore.Authorization;
 using Microsoft.AspNetCore.Cors;
 using Microsoft.AspNetCore.Mvc;
 using Microsoft.AspNetCore.Mvc.Filters;
+using Newtonsoft.Json.Linq;
 using CustodianAccountData = BTCPayServer.Data.CustodianAccountData;
 using CustodianAccountDataClient = BTCPayServer.Client.Models.CustodianAccountData;
 
@@ -80,10 +82,51 @@ namespace BTCPayServer.Controllers.Greenfield
         public async Task<IActionResult> ViewCustodianAccount(string storeId, string accountId,
             [FromQuery] bool assetBalances = false, CancellationToken cancellationToken = default)
         {
-            var custodianAccountData = await GetCustodian(storeId, accountId);
+            var custodianAccountData = await GetCustodianAccount(storeId, accountId);
+            if (custodianAccountData == null)
+            {
+                return this.CreateAPIError(404, "custodian-account-not-found", "The custodian account was not found.");
+            }
             var custodianAccount = await ToModel(custodianAccountData, assetBalances, cancellationToken);
             return Ok(custodianAccount);
         }
+        
+        // [HttpGet("~/api/v1/stores/{storeId}/custodian-accounts/{accountId}/config")]
+        // [Authorize(Policy = Policies.CanManageCustodianAccounts,
+        //     AuthenticationSchemes = AuthenticationSchemes.Greenfield)]
+        // public async Task<IActionResult> FetchCustodianAccountConfigForm(string storeId, string accountId,
+        //     [FromQuery] string locale = "en-US", CancellationToken cancellationToken = default)
+        // {
+        //     // TODO this endpoint needs tests
+        //     var custodianAccountData = await GetCustodianAccount(storeId, accountId);
+        //     var custodianAccount = await ToModel(custodianAccountData, false, cancellationToken);
+        //     
+        //     var custodian = GetCustodianByCode(custodianAccount.CustodianCode);
+        //     var form = await custodian.GetConfigForm(custodianAccount.Config, locale, cancellationToken);
+        //         
+        //     return Ok(form);
+        // }
+        //
+        // [HttpPost("~/api/v1/stores/{storeId}/custodian-accounts/{accountId}/config")]
+        // [Authorize(Policy = Policies.CanManageCustodianAccounts,
+        //     AuthenticationSchemes = AuthenticationSchemes.Greenfield)]
+        // public async Task<IActionResult> PostCustodianAccountConfigForm(string storeId, string accountId, JObject values,
+        //     [FromQuery] string locale = "en-US", CancellationToken cancellationToken = default)
+        // {
+        //     // TODO this endpoint needs tests
+        //     var custodianAccountData = await GetCustodianAccount(storeId, accountId);
+        //     var custodianAccount = await ToModel(custodianAccountData, false, cancellationToken);
+        //     
+        //     var custodian = GetCustodianByCode(custodianAccount.CustodianCode);
+        //     var form = await custodian.GetConfigForm(values, locale, cancellationToken);
+        //     
+        //     if (form.IsValid())
+        //     {
+        //         // TODO save the data to the config so it is persisted
+        //     }
+        //     
+        //     return Ok(form);
+        // }
 
         private async Task<bool> CanSeeCustodianAccountConfig()
         {
@@ -138,7 +181,7 @@ namespace BTCPayServer.Controllers.Greenfield
         {
             request ??= new CreateCustodianAccountRequest();
 
-            var custodianAccount = await GetCustodian(storeId, accountId);
+            var custodianAccount = await GetCustodianAccount(storeId, accountId);
             var custodian = GetCustodianByCode(request.CustodianCode);
 
             // TODO If storeId is not valid, we get a foreign key SQL error. Is this okay or do we want to check the storeId first?
@@ -171,7 +214,7 @@ namespace BTCPayServer.Controllers.Greenfield
             AuthenticationSchemes = AuthenticationSchemes.Greenfield)]
         public async Task<IActionResult> GetDepositAddress(string storeId, string accountId, string paymentMethod, CancellationToken cancellationToken = default)
         {
-            var custodianAccount = await GetCustodian(storeId, accountId);
+            var custodianAccount = await GetCustodianAccount(storeId, accountId);
             var custodian = GetCustodianByCode(custodianAccount.CustodianCode);
             var config = custodianAccount.GetBlob();
 
@@ -198,7 +241,7 @@ namespace BTCPayServer.Controllers.Greenfield
                     $"Please use 'BTC' instead of 'SATS'.");
             }
 
-            var custodianAccount = await GetCustodian(storeId, accountId);
+            var custodianAccount = await GetCustodianAccount(storeId, accountId);
             var custodian = GetCustodianByCode(custodianAccount.CustodianCode);
 
             if (custodian is ICanTrade tradableCustodian)
@@ -248,7 +291,7 @@ namespace BTCPayServer.Controllers.Greenfield
                     $"Please use 'BTC' instead of 'SATS'.");
             }
 
-            var custodianAccount = await GetCustodian(storeId, accountId);
+            var custodianAccount = await GetCustodianAccount(storeId, accountId);
 
             var custodian = GetCustodianByCode(custodianAccount.CustodianCode);
 
@@ -267,7 +310,7 @@ namespace BTCPayServer.Controllers.Greenfield
             AuthenticationSchemes = AuthenticationSchemes.Greenfield)]
         public async Task<IActionResult> GetTradeInfo(string storeId, string accountId, string tradeId, CancellationToken cancellationToken = default)
         {
-            var custodianAccount = await GetCustodian(storeId, accountId);
+            var custodianAccount = await GetCustodianAccount(storeId, accountId);
             var custodian = GetCustodianByCode(custodianAccount.CustodianCode);
 
             if (custodian is ICanTrade tradableCustodian)
@@ -292,7 +335,7 @@ namespace BTCPayServer.Controllers.Greenfield
         public async Task<IActionResult> CreateWithdrawal(string storeId, string accountId,
             WithdrawRequestData request, CancellationToken cancellationToken = default)
         {
-            var custodianAccount = await GetCustodian(storeId, accountId);
+            var custodianAccount = await GetCustodianAccount(storeId, accountId);
             var custodian = GetCustodianByCode(custodianAccount.CustodianCode);
 
             if (custodian is ICanWithdraw withdrawableCustodian)
@@ -309,7 +352,7 @@ namespace BTCPayServer.Controllers.Greenfield
         }
 
 
-        async Task<CustodianAccountData> GetCustodian(string storeId, string accountId)
+        async Task<CustodianAccountData> GetCustodianAccount(string storeId, string accountId)
         {
             var cust = await _custodianAccountRepository.FindById(storeId, accountId);
             if (cust is null)
@@ -335,7 +378,7 @@ namespace BTCPayServer.Controllers.Greenfield
             AuthenticationSchemes = AuthenticationSchemes.Greenfield)]
         public async Task<IActionResult> GetWithdrawalInfo(string storeId, string accountId, string paymentMethod, string withdrawalId, CancellationToken cancellationToken = default)
         {
-            var custodianAccount = await GetCustodian(storeId, accountId);
+            var custodianAccount = await GetCustodianAccount(storeId, accountId);
             var custodian = GetCustodianByCode(custodianAccount.CustodianCode);
 
             if (custodian is ICanWithdraw withdrawableCustodian)

BTCPayServer/Controllers/LnurlAuthService.cs

@@ -75,7 +75,7 @@ namespace BTCPayServer
                 CreationStore.Remove(userId, out _);
                 return true;
             }
-            catch (Exception)
+            catch (Exception e)
             {
                 return false;
             }

BTCPayServer/Controllers/UICustodianAccountsController.cs

@@ -0,0 +1,340 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Threading.Tasks;
+using BTCPayServer.Abstractions.Constants;
+using BTCPayServer.Abstractions.Custodians;
+using BTCPayServer.Abstractions.Extensions;
+using BTCPayServer.Abstractions.Form;
+using BTCPayServer.Client;
+using BTCPayServer.Data;
+using BTCPayServer.Filters;
+using BTCPayServer.Models.CustodianAccountViewModels;
+using BTCPayServer.Services.Custodian.Client;
+using BTCPayServer.Services.Rates;
+using Microsoft.AspNetCore.Authorization;
+using Microsoft.AspNetCore.Identity;
+using Microsoft.AspNetCore.Mvc;
+using Newtonsoft.Json.Linq;
+using CustodianAccountData = BTCPayServer.Data.CustodianAccountData;
+using StoreData = BTCPayServer.Data.StoreData;
+
+namespace BTCPayServer.Controllers
+{
+    [Authorize(Policy = Policies.CanModifyStoreSettings, AuthenticationSchemes = AuthenticationSchemes.Cookie)]
+    [AutoValidateAntiforgeryToken]
+    [ExperimentalRouteAttribute]
+    public class UICustodianAccountsController : Controller
+    {
+        public UICustodianAccountsController(
+            CurrencyNameTable currencyNameTable,
+            UserManager<ApplicationUser> userManager,
+            CustodianAccountRepository custodianAccountRepository,
+            IEnumerable<ICustodian> custodianRegistry
+        )
+        {
+            _currencyNameTable = currencyNameTable ?? throw new ArgumentNullException(nameof(currencyNameTable));
+            _userManager = userManager;
+            _custodianAccountRepository = custodianAccountRepository;
+            _custodianRegistry = custodianRegistry;
+        }
+
+        private readonly IEnumerable<ICustodian> _custodianRegistry;
+        private readonly UserManager<ApplicationUser> _userManager;
+        private readonly CustodianAccountRepository _custodianAccountRepository;
+        private readonly CurrencyNameTable _currencyNameTable;
+
+        public string CreatedCustodianAccountId { get; set; }
+
+        [HttpGet("/stores/{storeId}/custodian-accounts/{accountId}")]
+        public async Task<IActionResult> ViewCustodianAccount(string storeId, string accountId)
+        {
+            var vm = new ViewCustodianAccountViewModel();
+            var custodianAccount = await _custodianAccountRepository.FindById(storeId, accountId);
+
+            if (custodianAccount == null)
+                return NotFound();
+
+            var custodian = _custodianRegistry.GetCustodianByCode(custodianAccount.CustodianCode);
+            if (custodian == null)
+            {
+                // TODO The custodian account is broken. The custodian is no longer available. Maybe delete the custodian account?
+                return NotFound();
+            }
+
+            vm.Custodian = custodian;
+            vm.CustodianAccount = custodianAccount;
+            var store = GetCurrentStore();
+            var storeBlob = BTCPayServer.Data.StoreDataExtensions.GetStoreBlob(store);
+            var defaultCurrency = storeBlob.DefaultCurrency;
+            vm.DefaultCurrency = defaultCurrency;
+
+
+            try
+            {
+                var assetBalances = new Dictionary<string, AssetBalanceInfo>();
+                var assetBalancesData =
+                    await custodian.GetAssetBalancesAsync(custodianAccount.GetBlob(), cancellationToken: default);
+
+                foreach (var pair in assetBalancesData)
+                {
+                    var asset = pair.Key;
+
+                    assetBalances.Add(asset,
+                        new AssetBalanceInfo { Asset = asset, Qty = pair.Value }
+                    );
+                }
+
+
+                if (custodian is ICanTrade tradingCustodian)
+                {
+                    var config = custodianAccount.GetBlob();
+                    var tradableAssetPairs = tradingCustodian.GetTradableAssetPairs();
+
+                    foreach (var pair in assetBalances)
+                    {
+                        var asset = pair.Key;
+                        var assetBalance = assetBalances[asset];
+
+                        if (asset.Equals(defaultCurrency))
+                        {
+                            assetBalance.FormattedFiatValue = _currencyNameTable.DisplayFormatCurrency(pair.Value.Qty, defaultCurrency);
+                        }
+                        else
+                        {
+                            try
+                            {
+                                var quote = await tradingCustodian.GetQuoteForAssetAsync(defaultCurrency, asset,
+                                    config, default);
+                                assetBalance.Bid = quote.Bid;
+                                assetBalance.Ask = quote.Ask;
+                                assetBalance.FiatAsset = defaultCurrency;
+                                assetBalance.FormattedBid = _currencyNameTable.DisplayFormatCurrency(quote.Bid, quote.FromAsset);
+                                assetBalance.FormattedAsk = _currencyNameTable.DisplayFormatCurrency(quote.Ask, quote.FromAsset);
+                                assetBalance.FormattedFiatValue = _currencyNameTable.DisplayFormatCurrency(pair.Value.Qty * quote.Bid, pair.Value.FiatAsset);
+                                assetBalance.TradableAssetPairs = tradableAssetPairs.Where(o => o.AssetBought == asset || o.AssetSold == asset);
+                            }
+                            catch (WrongTradingPairException e)
+                            {
+                                // Cannot trade this asset, just ignore
+                            }
+                        }
+                    }
+                }
+
+                if (custodian is ICanWithdraw withdrawableCustodian)
+                {
+                    var withdrawableePaymentMethods = withdrawableCustodian.GetWithdrawablePaymentMethods();
+                    foreach (var withdrawableePaymentMethod in withdrawableePaymentMethods)
+                    {
+                        var withdrawableAsset = withdrawableePaymentMethod.Split("-")[0];
+                        if (assetBalances.ContainsKey(withdrawableAsset))
+                        {
+                            var assetBalance = assetBalances[withdrawableAsset];
+                            assetBalance.CanWithdraw = true;
+                        }
+                    }
+                }
+
+                if (custodian is ICanDeposit depositableCustodian)
+                {
+                    var depositablePaymentMethods = depositableCustodian.GetDepositablePaymentMethods();
+                    foreach (var depositablePaymentMethod in depositablePaymentMethods)
+                    {
+                        var depositableAsset = depositablePaymentMethod.Split("-")[0];
+                        if (assetBalances.ContainsKey(depositableAsset))
+                        {
+                            var assetBalance = assetBalances[depositableAsset];
+                            assetBalance.CanDeposit = true;
+                        }
+                    }
+                }
+
+                vm.AssetBalances = assetBalances;
+            }
+            catch (Exception e)
+            {
+                vm.GetAssetBalanceException = e;
+            }
+
+            return View(vm);
+        }
+
+        [HttpGet("/stores/{storeId}/custodian-accounts/{accountId}/edit")]
+        public async Task<IActionResult> EditCustodianAccount(string storeId, string accountId)
+        {
+            var custodianAccount = await _custodianAccountRepository.FindById(storeId, accountId);
+            if (custodianAccount == null)
+                return NotFound();
+
+            var custodian = _custodianRegistry.GetCustodianByCode(custodianAccount.CustodianCode);
+            if (custodian == null)
+            {
+                // TODO The custodian account is broken. The custodian is no longer available. Maybe delete the custodian account?
+                return NotFound();
+            }
+            var configForm = await custodian.GetConfigForm(custodianAccount.GetBlob(), "en-US");
+
+            var vm = new EditCustodianAccountViewModel();
+            vm.CustodianAccount = custodianAccount;
+            vm.ConfigForm = configForm;
+            return View(vm);
+        }
+
+        [HttpPost("/stores/{storeId}/custodian-accounts/{accountId}/edit")]
+        public async Task<IActionResult> EditCustodianAccount(string storeId, string accountId,
+            EditCustodianAccountViewModel vm)
+        {
+            // The locale is not important yet, but keeping it here so we can find it easily when localization becomes a thing.
+            var locale = "en-US";
+
+            var custodianAccount = await _custodianAccountRepository.FindById(storeId, accountId);
+            if (custodianAccount == null)
+                return NotFound();
+
+            var custodian = _custodianRegistry.GetCustodianByCode(custodianAccount.CustodianCode);
+            if (custodian == null)
+            {
+                // TODO The custodian account is broken. The custodian is no longer available. Maybe delete the custodian account?
+                return NotFound();
+            }
+            var configForm = await custodian.GetConfigForm(custodianAccount.GetBlob(), locale);
+
+            var newData = new JObject();
+            foreach (var pair in Request.Form)
+            {
+                if ("CustodianAccount.Name".Equals(pair.Key))
+                {
+                    custodianAccount.Name = pair.Value;
+                }
+                else
+                {
+                    // TODO support posted array notation, like a field called "WithdrawToAddressNamePerPaymentMethod[BTC-OnChain]". The data should be nested in the JSON.
+                    newData.Add(pair.Key, pair.Value.ToString());
+                }
+            }
+
+            var newConfigData = RemoveUnusedFieldsFromConfig(custodianAccount.GetBlob(), newData, configForm);
+            var newConfigForm = await custodian.GetConfigForm(newConfigData, locale);
+
+            if (newConfigForm.IsValid())
+            {
+                custodianAccount.SetBlob(newConfigData);
+                custodianAccount = await _custodianAccountRepository.CreateOrUpdate(custodianAccount);
+
+                return RedirectToAction(nameof(ViewCustodianAccount),
+                    new { storeId = custodianAccount.StoreId, accountId = custodianAccount.Id });
+            }
+
+            // Form not valid: The user must fix the errors before we can save
+            vm.CustodianAccount = custodianAccount;
+            vm.ConfigForm = newConfigForm;
+            return View(vm);
+        }
+
+
+        [HttpGet("/stores/{storeId}/custodian-accounts/create")]
+        public IActionResult CreateCustodianAccount(string storeId)
+        {
+            var vm = new CreateCustodianAccountViewModel();
+            vm.StoreId = storeId;
+            vm.SetCustodianRegistry(_custodianRegistry);
+            return View(vm);
+        }
+
+        [HttpPost("/stores/{storeId}/custodian-accounts/create")]
+        public async Task<IActionResult> CreateCustodianAccount(string storeId, CreateCustodianAccountViewModel vm)
+        {
+            var store = GetCurrentStore();
+            vm.StoreId = store.Id;
+            vm.SetCustodianRegistry(_custodianRegistry);
+
+            var custodian = _custodianRegistry.GetCustodianByCode(vm.SelectedCustodian);
+            if (custodian == null)
+            {
+                ModelState.AddModelError(nameof(vm.SelectedCustodian), "Invalid Custodian");
+                return View(vm);
+            }
+            if (string.IsNullOrEmpty(vm.Name))
+            {
+                vm.Name = custodian.Name;
+            }
+
+            var custodianAccountData = new CustodianAccountData { CustodianCode = vm.SelectedCustodian, StoreId = vm.StoreId, Name = custodian.Name };
+
+
+            var configData = new JObject();
+            foreach (var pair in Request.Form)
+            {
+                configData.Add(pair.Key, pair.Value.ToString());
+            }
+
+            var configForm = await custodian.GetConfigForm(configData, "en-US");
+            if (configForm.IsValid())
+            {
+                // configForm.removeUnusedKeys();
+                custodianAccountData.SetBlob(configData);
+                custodianAccountData = await _custodianAccountRepository.CreateOrUpdate(custodianAccountData);
+                TempData[WellKnownTempData.SuccessMessage] = "Custodian account successfully created";
+                CreatedCustodianAccountId = custodianAccountData.Id;
+
+                return RedirectToAction(nameof(ViewCustodianAccount),
+                    new { storeId = custodianAccountData.StoreId, accountId = custodianAccountData.Id });
+            }
+
+            // Ask for more data
+            vm.ConfigForm = configForm;
+            return View(vm);
+        }
+
+
+        [HttpGet("/stores/{storeId}/custodian-accounts/{accountId}/delete")]
+        public async Task<IActionResult> DeleteCustodianAccount(string storeId, string accountId)
+        {
+            var custodianAccount = await _custodianAccountRepository.FindById(storeId, accountId);
+            if (custodianAccount == null)
+            {
+                return NotFound();
+            }
+
+            var isDeleted = await _custodianAccountRepository.Remove(custodianAccount.Id, custodianAccount.StoreId);
+            if (isDeleted)
+            {
+                TempData[WellKnownTempData.SuccessMessage] = "Custodian account deleted";
+                return RedirectToAction("Dashboard", "UIStores", new { storeId });
+            }
+
+            TempData[WellKnownTempData.ErrorMessage] = "Could not delete custodian account";
+            return RedirectToAction(nameof(ViewCustodianAccount),
+                new { storeId = custodianAccount.StoreId, accountId = custodianAccount.Id });
+        }
+
+        // The JObject may contain too much data because we used ALL post values and this may be more than we needed.
+        // Because we don't know the form fields beforehand, we will filter out the superfluous data afterwards.
+        // We will keep all the old keys + merge the new keys as per the current form.
+        // Since the form can differ by circumstances, we will never remove any keys that were previously stored. We just limit what we add.
+        private JObject RemoveUnusedFieldsFromConfig(JObject storedData, JObject newData, Form form)
+        {
+            JObject filteredData = new JObject();
+            var storedKeys = new List<string>();
+            foreach (var item in storedData)
+            {
+                storedKeys.Add(item.Key);
+            }
+
+            var formKeys = form.GetAllNames();
+
+            foreach (var item in newData)
+            {
+                if (storedKeys.Contains(item.Key) || formKeys.Contains(item.Key))
+                {
+                    filteredData[item.Key] = item.Value;
+                }
+            }
+
+            return filteredData;
+        }
+
+        private StoreData GetCurrentStore() => HttpContext.GetStoreData();
+    }
+}

BTCPayServer/Data/CustodianAccountDataExtensions.cs

@@ -1,5 +1,3 @@
-using System;
-using NBXplorer;
 using Newtonsoft.Json.Linq;
 
 namespace BTCPayServer.Data;

BTCPayServer/Models/CustodianAccountViewModels/AssetBalanceInfo.cs

@@ -0,0 +1,21 @@
+using System;
+using System.Collections.Generic;
+using BTCPayServer.Client.Models;
+
+namespace BTCPayServer.Models.CustodianAccountViewModels;
+
+public class AssetBalanceInfo
+{
+    
+    public string Asset { get; set; }
+    public decimal? Bid { get; set; }
+    public decimal? Ask { get; set; }
+    public decimal Qty { get; set; }
+    public string FiatAsset { get; set; }
+    public string FormattedFiatValue { get; set; }
+    public IEnumerable<AssetPairData> TradableAssetPairs { get; set; }
+    public bool CanWithdraw { get; set; }
+    public bool CanDeposit { get; set; }
+    public string FormattedBid { get; set; }
+    public string FormattedAsk { get; set; }
+}

BTCPayServer/Models/CustodianAccountViewModels/CreateCustodianAccountViewModel.cs

@@ -0,0 +1,48 @@
+using System.Collections.Generic;
+using System.ComponentModel.DataAnnotations;
+using System.Linq;
+using BTCPayServer.Abstractions.Custodians;
+using BTCPayServer.Abstractions.Form;
+using Microsoft.AspNetCore.Mvc.Rendering;
+
+namespace BTCPayServer.Models.CustodianAccountViewModels
+{
+    public class CreateCustodianAccountViewModel
+    {
+        
+        public void SetCustodianRegistry(IEnumerable<ICustodian> custodianRegistry)
+        {
+            var choices = custodianRegistry.Select(o => new Format
+            {
+                Name = o.Name,
+                Value = o.Code
+            }).ToArray();
+            var chosen = choices.FirstOrDefault();
+            Custodians = new SelectList(choices, nameof(chosen.Value), nameof(chosen.Name), chosen);
+        }
+        
+        class Format
+        {
+            public string Name { get; set; }
+            public string Value { get; set; }
+        }
+        
+        [Required]
+        [MaxLength(50)]
+        [MinLength(1)]
+        [Display(Name = "Name")]
+        public string Name { get; set; }
+
+        [Display(Name = "Store")]
+        public string StoreId { get; set; }
+
+        [Required]
+        [Display(Name = "Custodian")]
+        public string SelectedCustodian { get; set; }
+        //
+        public SelectList Custodians { get; set; }
+        
+        public Form ConfigForm { get; set; }
+
+    }
+}

BTCPayServer/Models/CustodianAccountViewModels/EditCustodianAccountViewModel.cs

@@ -0,0 +1,12 @@
+using BTCPayServer.Abstractions.Form;
+using BTCPayServer.Data;
+
+namespace BTCPayServer.Models.CustodianAccountViewModels
+{
+    public class EditCustodianAccountViewModel
+    {
+
+        public CustodianAccountData CustodianAccount { get; set; }
+        public Form ConfigForm { get; set; }
+    }
+}

BTCPayServer/Models/CustodianAccountViewModels/ViewCustodianAccountViewModel.cs

@@ -0,0 +1,16 @@
+using System;
+using System.Collections.Generic;
+using BTCPayServer.Abstractions.Custodians;
+using BTCPayServer.Data;
+
+namespace BTCPayServer.Models.CustodianAccountViewModels
+{
+    public class ViewCustodianAccountViewModel
+    {
+        public ICustodian Custodian { get; set; }
+        public CustodianAccountData CustodianAccount { get; set; }
+        public Dictionary<string,AssetBalanceInfo> AssetBalances { get; set; }
+        public Exception GetAssetBalanceException { get; set; }
+        public string DefaultCurrency { get; set; }
+    }
+}

BTCPayServer/Services/Custodian/CustodianAccountRepository.cs

@@ -52,7 +52,6 @@ namespace BTCPayServer.Services.Custodian.Client
             await using var context = _contextFactory.CreateContext();
             IQueryable<CustodianAccountData> query = context.CustodianAccount
                 .Where(ca => ca.StoreId == storeId);
-            //.SelectMany(c => c.StoreData.Invoices);
 
             var data = await query.ToArrayAsync( cancellationToken).ConfigureAwait(false);
             return data;

BTCPayServer/Views/Shared/_Form.cshtml

@@ -0,0 +1,34 @@
+@model BTCPayServer.Abstractions.Form.Form
+
+@foreach (var fieldset in Model.Fieldsets)
+{
+    <fieldset>
+        <legend>@fieldset.Label</legend>
+        @foreach (var field in fieldset.Fields)
+        {
+@if ("text".Equals(field.Type))
+{
+    <div class="form-group">
+        @if (field.Required)
+        {
+            <label class="form-label" for="@field.Name" data-required>
+                @field.Label
+            </label>
+        }
+        else
+        {
+            <label class="form-label" for="@field.Name">
+                @field.Label
+            </label>
+        }
+
+        <input class="form-control @(@field.IsValid() ? "" : "is-invalid")" id="@field.Name" type="text" required="@field.Required" name="@field.Name" value="@field.Value" aria-describedby="HelpText@field.Name"/>
+        <small id="HelpText@field.Name" class="form-text text-muted">
+            @field.HelpText
+        </small>
+
+    </div>
+}
+        }
+    </fieldset>
+}

BTCPayServer/Views/Shared/_FormTopMessages.cshtml

@@ -0,0 +1,10 @@
+@model BTCPayServer.Abstractions.Form.Form
+@using ExchangeSharp
+
+@if (Model.TopMessages.Count > 0)
+{
+    @foreach (var alertMessage in Model.TopMessages)
+    {
+        <p class="alert alert-@alertMessage.Type.ToStringLowerInvariant()">@alertMessage.Message</p>
+    }
+}

BTCPayServer/Views/UICustodianAccounts/CreateCustodianAccount.cshtml

@@ -0,0 +1,60 @@
+@using BTCPayServer.Views.Apps
+@using Microsoft.AspNetCore.Mvc.TagHelpers
+@using BTCPayServer.Abstractions.Extensions
+@model BTCPayServer.Models.CustodianAccountViewModels.CreateCustodianAccountViewModel
+@{
+    ViewData.SetActivePage(AppsNavPages.Create, "Add a custodian account");
+}
+
+@section PageFootContent {
+    <partial name="_ValidationScriptsPartial" />
+}
+
+<partial name="_StatusMessage" />
+
+<h2 class="mt-1 mb-4">@ViewData["Title"]</h2>
+
+<div class="row">
+    <div class="col-xl-8 col-xxl-constrain">
+        <form asp-action="CreateCustodianAccount">
+            <div asp-validation-summary="ModelOnly" class="text-danger"></div>
+            
+            @if (!string.IsNullOrEmpty(Model.SelectedCustodian))
+            {
+                <partial name="_FormTopMessages" model="Model.ConfigForm" />
+            }
+            else if(Model.Custodians.Count() > 0)
+            {
+                <div class="form-group">
+                    <label asp-for="SelectedCustodian" class="form-label" data-required></label>
+                    <select asp-for="SelectedCustodian" asp-items="Model.Custodians" class="form-select"></select>
+                </div>
+            }
+            else
+            {
+                <p>No custodians available. Install some plugins to add custodian / exchange support.</p>
+            }
+            
+            @if (!string.IsNullOrEmpty(Model.SelectedCustodian))
+            {
+                <div class="form-group">
+                    <label asp-for="SelectedCustodian" class="form-label" data-required></label>
+                    <select disabled asp-for="SelectedCustodian" asp-items="Model.Custodians" class="form-select"></select>
+                    <input type="hidden" asp-for="SelectedCustodian" />
+                </div>
+                
+                <div class="form-group">
+                    <label asp-for="Name" class="form-label" data-required></label>
+                    <input asp-for="Name" class="form-control" required/>
+                    <span asp-validation-for="Name" class="text-danger"></span>
+                </div>
+
+                <partial name="_Form" model="Model.ConfigForm" />
+            }
+            
+            <div class="form-group mt-4">
+                <input type="submit" value="Continue" class="btn btn-primary" id="Continue" />
+            </div>
+        </form>
+    </div>
+</div>

BTCPayServer/Views/UICustodianAccounts/CustodianAccountsNavPages.cs

@@ -0,0 +1,7 @@
+namespace BTCPayServer.Views.CustodianAccounts
+{
+    public enum CustodianAccountsNavPages
+    {
+        View, Create, Update
+    }
+}

BTCPayServer/Views/UICustodianAccounts/EditCustodianAccount.cshtml

@@ -0,0 +1,37 @@
+@using BTCPayServer.Views.Apps
+@using Microsoft.AspNetCore.Mvc.TagHelpers
+@using BTCPayServer.Abstractions.Extensions
+@model BTCPayServer.Models.CustodianAccountViewModels.EditCustodianAccountViewModel
+@{
+    ViewData.SetActivePage(AppsNavPages.Update, "Edit custodian account");
+}
+
+@section PageFootContent {
+    <partial name="_ValidationScriptsPartial"/>
+}
+
+<partial name="_StatusMessage"/>
+
+<h2 class="mt-1 mb-4">@ViewData["Title"]</h2>
+
+<div class="row">
+    <div class="col-xl-8 col-xxl-constrain">
+        <form asp-action="EditCustodianAccount">
+            <div asp-validation-summary="ModelOnly" class="text-danger"></div>
+            
+            <partial name="_FormTopMessages" model="Model.ConfigForm"/>
+
+            <div class="form-group">
+                <label asp-for="CustodianAccount.Name" class="form-label" data-required></label>
+                <input asp-for="CustodianAccount.Name" class="form-control" required/>
+                <span asp-validation-for="CustodianAccount.Name" class="text-danger"></span>
+            </div>
+
+            <partial name="_Form" model="Model.ConfigForm"/>
+
+            <div class="form-group mt-4">
+                <input type="submit" value="Continue" class="btn btn-primary" id="Save"/>
+            </div>
+        </form>
+    </div>
+</div>

BTCPayServer/Views/UICustodianAccounts/ViewCustodianAccount.cshtml

@@ -0,0 +1,190 @@
+@using BTCPayServer.Views.Apps
+@using Microsoft.AspNetCore.Mvc.TagHelpers
+@using BTCPayServer.Abstractions.Extensions
+@using BTCPayServer.Abstractions.Custodians
+@model BTCPayServer.Models.CustodianAccountViewModels.ViewCustodianAccountViewModel
+@{
+    ViewData.SetActivePage(AppsNavPages.Create, "Custodian account: " + @Model?.CustodianAccount.Name);
+}
+
+@section PageFootContent {
+    <partial name="_ValidationScriptsPartial"/>
+}
+
+
+<partial name="_StatusMessage"/>
+
+<div class="sticky-header-setup"></div>
+<div class="sticky-header d-sm-flex align-items-center justify-content-between">
+    <h2 class="mb-0">
+        @ViewData["Title"]
+    </h2>
+    <div class="d-flex gap-3 mt-3 mt-sm-0">
+        <a asp-action="EditCustodianAccount" asp-route-storeId="@Model.CustodianAccount.StoreId" asp-route-accountId="@Model.CustodianAccount.Id" class="btn btn-primary mt-3 mt-sm-0" role="button" id="EditCustodianAccountConfig">
+            <span class="fa fa-gear"></span> Configure
+        </a>
+        <a asp-action="DeleteCustodianAccount" asp-route-storeId="@Model.CustodianAccount.StoreId" asp-route-accountId="@Model.CustodianAccount.Id" class="btn btn-danger mt-3 mt-sm-0" role="button" id="DeleteCustodianAccountConfig">
+            <span class="fa fa-trash"></span> Delete
+        </a>
+        <!--
+        <button type="submit" class="btn btn-primary order-sm-1" id="SaveSettings">Save</button>
+        <a class="btn btn-secondary" id="ViewApp" target="app_" href="/apps/MQ2sCVsmQ95JBZ4aZDtoSwMAnBY/pos">View</a>
+        -->
+    </div>
+
+</div>
+
+<div class="row">
+    <div class="col-xl-12">
+
+        @if (@Model.GetAssetBalanceException != null)
+        {
+            <p class="alert alert-danger">
+                @Model.GetAssetBalanceException.Message
+            </p>
+        }
+
+        <h2>Balances</h2>
+        <div class="table-responsive">
+            <table class="table table-hover table-responsive-md">
+                <thead>
+                <tr>
+                    <th>Asset</th>
+                    <th class="text-end">Balance</th>
+                    <th class="text-end">Unit Price (Bid)</th>
+                    <th class="text-end">Unit Price (Ask)</th>
+                    <th class="text-end">Fiat Value</th>
+                    <th class="text-end">Actions</th>
+                </tr>
+                </thead>
+                <tbody>
+                @if (Model.AssetBalances != null && Model.AssetBalances.Count > 0)
+                {
+                    @foreach (var pair in Model.AssetBalances.OrderBy(key => key.Key))
+                    {
+                        <tr>
+                            <td>@pair.Key</td>
+                            <!-- TODO format as number? How? -->
+                            <th class="text-end">@pair.Value.Qty</th>
+                            <th class="text-end">
+                                @pair.Value.FormattedBid
+                            </th>
+                            <th class="text-end">
+                                @pair.Value.FormattedAsk
+                            </th>
+                            <th class="text-end">
+                                @(pair.Value.FormattedFiatValue)
+                            </th>
+                            <th class="text-end">
+                                @if (pair.Value.TradableAssetPairs != null)
+                                {
+                                    <a data-bs-toggle="modal" data-bs-target="#tradeModal" href="#">Trade</a>
+                                }
+                                @if (pair.Value.CanDeposit)
+                                {
+                                    <a data-bs-toggle="modal" data-bs-target="#depositModal" href="#">Deposit</a>
+                                }
+                                @if (pair.Value.CanWithdraw)
+                                {
+                                    <a data-bs-toggle="modal" data-bs-target="#withdrawModal" href="#">Withdraw</a>
+                                }
+                            </th>
+                        </tr>
+                    }
+                }
+                else if (Model.GetAssetBalanceException == null)
+                {
+                    <tr>
+                        <td colspan="999" class="text-center">No assets are stored with this custodian (yet).</td>
+                    </tr>
+                }
+                else
+                {
+                    <tr>
+                        <td colspan="999" class="text-center">An error occured while loading assets and balances.</td>
+                    </tr>
+                }
+                </tbody>
+            </table>
+        </div>
+
+
+        <h2>Features</h2>
+        <p>The @Model.Custodian.Name custodian supports:</p>
+        <ul>
+            <li>Viewing asset balances</li>
+            @if (Model.Custodian is ICanTrade)
+            {
+                <li>Trading (Greenfield API only, for now)</li>
+            }
+            @if (Model.Custodian is ICanDeposit)
+            {
+                <li>Depositing (Greenfield API only, for now)</li>
+            }
+            @if (Model.Custodian is ICanWithdraw)
+            {
+                <li>Withdrawing (Greenfield API only, for now)</li>
+            }
+        </ul>
+
+
+    </div>
+</div>
+
+
+<div class="modal" tabindex="-1" role="dialog" id="withdrawModal">
+    <div class="modal-dialog" role="document">
+        <div class="modal-content">
+            <div class="modal-header">
+                <h5 class="modal-title">Withdraw</h5>
+                <button type="button" class="btn-close" data-bs-dismiss="modal" aria-label="Close">
+                    <vc:icon symbol="close"/>
+                </button>
+            </div>
+            <div class="modal-body">
+                <p>Withdrawals are coming soon, but if you need this today, you can use our <a rel="noopener noreferrer" href="https://docs.btcpayserver.org/API/Greenfield/v1/" target="_blank">Greenfield API "Withdraw to store wallet" endpoint</a> to execute a withdrawal.</p>
+            </div>
+            <div class="modal-footer">
+                <button type="button" class="btn btn-secondary" data-bs-dismiss="modal">Close</button>
+            </div>
+        </div>
+    </div>
+</div>
+
+<div class="modal" tabindex="-1" role="dialog" id="depositModal">
+    <div class="modal-dialog" role="document">
+        <div class="modal-content">
+            <div class="modal-header">
+                <h5 class="modal-title">Deposit</h5>
+                <button type="button" class="btn-close" data-bs-dismiss="modal" aria-label="Close">
+                    <vc:icon symbol="close"/>
+                </button>
+            </div>
+            <div class="modal-body">
+                <p>Deposits are coming soon, but if you need this today, you can use our <a rel="noopener noreferrer" href="https://docs.btcpayserver.org/API/Greenfield/v1/" target="_blank">Greenfield API "Get a deposit address for custodian" endpoint</a> to get a deposit address to send your assets to.</p>
+            </div>
+            <div class="modal-footer">
+                <button type="button" class="btn btn-secondary" data-bs-dismiss="modal">Close</button>
+            </div>
+        </div>
+    </div>
+</div>
+
+<div class="modal" tabindex="-1" role="dialog" id="tradeModal">
+    <div class="modal-dialog" role="document">
+        <div class="modal-content">
+            <div class="modal-header">
+                <h5 class="modal-title">Trade</h5>
+                <button type="button" class="btn-close" data-bs-dismiss="modal" aria-label="Close">
+                    <vc:icon symbol="close"/>
+                </button>
+            </div>
+            <div class="modal-body">
+                <p>Trades are coming soon, but if you need this today, you can use our <a rel="noopener noreferrer" href="https://docs.btcpayserver.org/API/Greenfield/v1/" target="_blank"> Greenfield API "Trade one asset for another" endpoint</a> to convert an asset to another via a market order.</p>
+            </div>
+            <div class="modal-footer">
+                <button type="button" class="btn btn-secondary" data-bs-dismiss="modal">Close</button>
+            </div>
+        </div>
+    </div>
+</div>

Plugins/BTCPayServer.Plugins.Custodians.FakeCustodian/BTCPayServer.Plugins.Custodians.FakeCustodian.csproj

@@ -0,0 +1,14 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+    <PropertyGroup>
+        <TargetFramework>net6.0</TargetFramework>
+        <ImplicitUsings>enable</ImplicitUsings>
+        <Nullable>enable</Nullable>
+        <RootNamespace>BTCPayServer.Plugins.Custodians.FakeCustodian</RootNamespace>
+    </PropertyGroup>
+
+    <ItemGroup>
+      <ProjectReference Include="..\..\BTCPayServer.Abstractions\BTCPayServer.Abstractions.csproj" />
+    </ItemGroup>
+
+</Project>

Plugins/BTCPayServer.Plugins.Custodians.FakeCustodian/FakeCustodian.cs

@@ -0,0 +1,75 @@
+using BTCPayServer.Abstractions.Custodians;
+using BTCPayServer.Abstractions.Form;
+using Newtonsoft.Json.Linq;
+
+namespace BTCPayServer.Plugins.Custodians.FakeCustodian;
+
+public class FakeCustodian : ICustodian
+{
+    public string Code
+    {
+        get => "fake";
+    }
+
+    public string Name
+    {
+        get => "Fake Exchange";
+    }
+
+    public Task<Dictionary<string, decimal>> GetAssetBalancesAsync(JObject config, CancellationToken cancellationToken)
+    {
+        var fakeConfig = ParseConfig(config);
+        var r = new Dictionary<string, decimal>()
+        {
+            { "BTC", fakeConfig.BTCBalance },
+            { "LTC", fakeConfig.LTCBalance },
+            { "USD", fakeConfig.USDBalance },
+            { "EUR", fakeConfig.EURBalance }
+        };
+        return Task.FromResult(r);
+    }
+
+    public Task<Form> GetConfigForm(JObject config, string locale, CancellationToken cancellationToken = default)
+    {
+        var fakeConfig = ParseConfig(config);
+
+        var form = new Form();
+        var fieldset = new Fieldset();
+
+        // Maybe a decimal type field would be better?
+        var fakeBTCBalance = new TextField("BTC Balance", "BTCBalance", fakeConfig?.BTCBalance.ToString(), true,
+            "Enter the amount of BTC you want to have.");
+        var fakeLTCBalance = new TextField("LTC Balance", "LTCBalance", fakeConfig?.LTCBalance.ToString(), true,
+            "Enter the amount of LTC you want to have.");
+        var fakeEURBalance = new TextField("EUR Balance", "EURBalance", fakeConfig?.EURBalance.ToString(), true,
+            "Enter the amount of EUR you want to have.");
+        var fakeUSDBalance = new TextField("USD Balance", "USDBalance", fakeConfig?.USDBalance.ToString(), true,
+            "Enter the amount of USD you want to have.");
+
+        fieldset.Label = "Your fake balances";
+        fieldset.Fields.Add(fakeBTCBalance);
+        fieldset.Fields.Add(fakeLTCBalance);
+        fieldset.Fields.Add(fakeEURBalance);
+        fieldset.Fields.Add(fakeUSDBalance);
+        form.Fieldsets.Add(fieldset);
+
+        return Task.FromResult(form);
+    }
+
+    private FakeCustodianConfig? ParseConfig(JObject config)
+    {
+        return config?.ToObject<FakeCustodianConfig>();
+    }
+}
+
+public class FakeCustodianConfig
+{
+    public decimal BTCBalance { get; set; }
+    public decimal LTCBalance { get; set; }
+    public decimal USDBalance { get; set; }
+    public decimal EURBalance { get; set; }
+
+    public FakeCustodianConfig()
+    {
+    }
+}

Plugins/BTCPayServer.Plugins.Custodians.FakeCustodian/FakeCustodianPlugin.cs

@@ -0,0 +1,19 @@
+using BTCPayServer.Abstractions.Custodians;
+using BTCPayServer.Abstractions.Models;
+using Microsoft.Extensions.DependencyInjection;
+
+namespace BTCPayServer.Plugins.Custodians.FakeCustodian
+{
+    public class FakeCustodianPlugin : BaseBTCPayServerPlugin
+    {
+        public override string Identifier { get; } = "BTCPayServer.Plugins.Custodians.Fake";
+        public override string Name { get; } = "Custodian: Fake";
+        public override string Description { get; } = "Adds a fake custodian for testing";
+
+        public override void Execute(IServiceCollection services)
+        {
+            services.AddSingleton<FakeCustodian>();
+            services.AddSingleton<ICustodian, FakeCustodian>(provider => provider.GetRequiredService<FakeCustodian>());
+        }
+    }
+}

btcpayserver.sln

@@ -37,6 +37,8 @@ Project("{2150E333-8FDC-42A3-9474-1A3956D46DE8}") = "Plugins", "Plugins", "{1FC7
 EndProject
 Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "BTCPayServer.PluginPacker", "BTCPayServer.PluginPacker\BTCPayServer.PluginPacker.csproj", "{7DC94B25-1CFC-4170-AA41-7BA983E4C0B8}"
 EndProject
+Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "BTCPayServer.Plugins.Custodians.FakeCustodian", "Plugins\BTCPayServer.Plugins.Custodians.FakeCustodian\BTCPayServer.Plugins.Custodians.FakeCustodian.csproj", "{49E1FE45-FE71-49DF-8701-8394E974BE82}"
+EndProject
 Global
 	GlobalSection(SolutionConfigurationPlatforms) = preSolution
 		Altcoins-Debug|Any CPU = Altcoins-Debug|Any CPU