Different message for admin deletion, check not to delete last admin

Ref: #549, #550

BTCPayServer/Controllers/ServerController.cs

@@ -383,12 +383,29 @@ namespace BTCPayServer.Controllers
             var user = userId == null ? null : await _UserManager.FindByIdAsync(userId);
             if (user == null)
                 return NotFound();
-            return View("Confirm", new ConfirmModel()
+
+            var admins = await _UserManager.GetUsersInRoleAsync(Roles.ServerAdmin);
+            if (admins.Count == 1)
             {
-                Title = "Delete user " + user.Email,
-                Description = "This user will be permanently deleted",
-                Action = "Delete"
-            });
+                // return
+                return View("Confirm", new ConfirmModel("Unable to Delete Last Admin",
+                    "This is the last Admin, so it can't be removed"));
+            }
+
+
+            var roles = await _UserManager.GetRolesAsync(user);
+            if (IsAdmin(roles))
+            {
+                return View("Confirm", new ConfirmModel("Delete Admin " + user.Email,
+                    "Are you sure you want to delete this Admin and delete all accounts, users and data associated with the server account?",
+                    "Delete"));
+            }
+            else
+            {
+                return View("Confirm", new ConfirmModel("Delete user " + user.Email,
+                                    "This user will be permanently deleted",
+                                    "Delete"));
+            }
         }
 
         [Route("server/users/{userId}/delete")]

BTCPayServer/Models/ConfirmModel.cs

@@ -7,6 +7,15 @@ namespace BTCPayServer.Models
 {
     public class ConfirmModel
     {
+        public ConfirmModel() { }
+
+        public ConfirmModel(string title, string desc, string action = null)
+        {
+            Title = title;
+            Description = desc;
+            Action = action;
+        }
+
         public string Title
         {
             get; set;

BTCPayServer/Views/Shared/Confirm.cshtml

@@ -12,6 +12,8 @@
                 <p>@Model.Description</p>
             </div>
         </div>
+        @if (!String.IsNullOrEmpty(Model.Action))
+        {
         <div class="row">
             <div class="col-lg-12 text-center">
                 <form method="post">
@@ -19,5 +21,6 @@
                 </form>
             </div>
         </div>
+        }
     </div>
 </section>