Add member "kind" - and refactor user "type" to "kind" for consistency (#16979)

* Rename UserType to UserKind

* Add MemberKind to tell API members from regular ones

* Remove user kind from invite user endpoint

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Co-authored-by: Mads Rasmussen <madsr@hey.com>

src/Umbraco.Infrastructure/Security/BackOfficeUserStore.cs

@@ -141,7 +141,7 @@ public class BackOfficeUserStore :
             StartMediaIds = user.StartMediaIds ?? new int[] { },
             IsLockedOut = user.IsLockedOut,
             Key = user.Key,
-            Type = user.Type
+            Kind = user.Kind
         };