New Backoffice: Fix feedback to users controller (#14031)

* Add specific not found results

* Add tests for the enable/disable not found tweak

* Cache ids and key in UserIdKeyResolver

* Don't cache null keys

* BackOffice not Backoffice

* Move fetching the user out of the ChangePasswordUsersController

* Move resolving user out of SetAvatar

* Move resolving user out of Update

* Return more specific notfound in bykey

* Use ErrorResult for all endpoints with unknown errors

* Split integration tests

* Add mappers

* Use ?: consistently

* Add reuseable iso code validator

* Validate ISO code

* Update supressions

* Use method from base to get current user key

* Rename ISo to Iso

* Use keys in services instead of user groups + Added a couple of new validations

---------

Co-authored-by: Bjarke Berg <mail@bergmania.dk>

src/Umbraco.Core/Security/ICoreBackOfficeUserManager.cs

@@ -0,0 +1,21 @@
+using Umbraco.Cms.Core.Models;
+using Umbraco.Cms.Core.Models.Membership;
+using Umbraco.Cms.Core.Services.OperationStatus;
+
+namespace Umbraco.Cms.Core.Security;
+
+public interface ICoreBackOfficeUserManager
+{
+    Task<IdentityCreationResult> CreateAsync(UserCreateModel createModel);
+
+    /// <summary>
+    /// Creates a user for an invite. This means that the password will not be populated with
+    /// </summary>
+    /// <param name="createModel"></param>
+    /// <returns></returns>
+    Task<IdentityCreationResult> CreateForInvite(UserCreateModel createModel);
+
+    Task<Attempt<string, UserOperationStatus>> GenerateEmailConfirmationTokenAsync(IUser user);
+
+    Task<Attempt<UserUnlockResult, UserOperationStatus>> UnlockUser(IUser user);
+}