* Onboarding: Invite new users
- Separates the user self-registration and invite cases
- Adds invitation email for users created by the admin
- Adds invitation tokens to verify user was invited
- Adds handler action for invite links
- Refactors `UserEventHostedService`
- Fixes#5726.
* Add permissioned form tag helper
* Better way of changing a user's role
* Test fixes
* Custom Forms
* Update BTCPayServer.Data/Migrations/20230125085242_AddForms.cs
* Cleanups
* Explain public form
* Add store branding
* Add form name to POS form
* add tests
* fix migration
* Minor cleanups
* Code improvements
* Add form validation
Closes#4317.
* Adapt form validation for Bootstrap 5
* update logic for forms
* pr changes
* Minor code cleanup
* Remove unused parameters
* Refactor Form data handling to avoid O(n3) issues
* Rename Hidden to Constant
* Pre-populate FormView from the query string params
* Fix test
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Co-authored-by: d11n <mail@dennisreimann.de>
Co-authored-by: nicolas.dorier <nicolas.dorier@gmail.com>
