Netcore: Fixes issues with user invites (#9616)

* AB9629
Fixes issues with user invites
- Issue with the generated link in the invite email
- Allow anonymous access to CurrentUserController.PostSetInvitedUserPassword, as it is used by users not logged in
- Allow anonymous access to AuthenticationController.GetPasswordConfig, as this is used to set a password for newly invited users, before they login

* Fix issues with invite flow

* Fix minor typos

* Fixed issue with validation response and remove/change avatar

* Fix issue with disable users, after all enums are handled like strings

* Fix tests

* Fix other validation issue

* Fix yet another validation issue

Co-authored-by: Elitsa Marinovska <elm@umbraco.dk>

src/Umbraco.Core/Models/SimpleValidationModel.cs

@@ -0,0 +1,16 @@
+using System.Collections.Generic;
+
+namespace Umbraco.Core.Models
+{
+    public class SimpleValidationModel
+    {
+        public SimpleValidationModel(IDictionary<string, object> modelState, string message = "The request is invalid.")
+        {
+            Message = message;
+            ModelState = modelState;
+        }
+
+        public string Message { get; }
+        public IDictionary<string, object> ModelState { get;  }
+    }
+}