Members and member types in the Management API (#15662)

* Members and member types in the Management API

* Add validation endpoints for members

* Include validation result in service response + add unit tests

* Regenerate OpenApi.json

* Regenerate OpenApi.json after merge

* Don't throw an exception when trying to set valid variation levels for member types

* Added missing ProducesResponseType

* Remove TODO, as that works

* Allow creation of member with explicit key

* Do not feature "parent" for member creation + add missing response type

* Do not feature a "Folder" in create member type (folders are not supported)

* Added missing build methods

* Fixed issue with mapping

---------

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

src/Umbraco.Core/Models/ContentEditing/MemberEditingModelBase.cs

@@ -0,0 +1,12 @@
+namespace Umbraco.Cms.Core.Models.ContentEditing;
+
+public abstract class MemberEditingModelBase : ContentEditingModelBase
+{
+    public bool IsApproved { get; set; }
+
+    public IEnumerable<string>? Roles { get; set; }
+
+    public string Email { get; set; } = string.Empty;
+
+    public string Username { get; set; } = string.Empty;
+}