Model mapping PoC (#15546)

* First take at new models for improved mapping between client and server

* Add variants to Media

* Re-introduced lost names

* Start breaking apart "Id" reference properties in request models as well

* Refactor to fix OpenAPI spec

* Discard TODO (not relevant)

* Split recycle bin response models

* Delete unused marker interface

* Use reference properties for content and media type handling

* Rework document and media types to be explicit in relations (do not expose "content type", it is an implementation detail)

* Mapping for document and media type copy + move

* Ensure correct response model for Media

* Regenerate OpenAPI JSON after forward merge

* Fix forward merge issues

* Fix forward merge + regenerate OpenApi.json

* Added unit tests for content state helper

* Move "allowed document types" endpoint to document type silo, refactored services and added "allowed media types"

* Regenerate OpenApi.json after forward merge

* Do not include content state for media items

* Review fix

src/Umbraco.Cms.Api.Management/Controllers/Tree/EntityTreeControllerBase.cs

@@ -1,6 +1,7 @@
 using Microsoft.AspNetCore.Mvc;
 using Umbraco.Cms.Api.Common.ViewModels.Pagination;
 using Umbraco.Cms.Api.Management.Services.Paging;
+using Umbraco.Cms.Api.Management.ViewModels;
 using Umbraco.Cms.Api.Management.ViewModels.Tree;
 using Umbraco.Cms.Core;
 using Umbraco.Cms.Core.Models;
@@ -115,12 +116,15 @@ public abstract class EntityTreeControllerBase<TItem> : ManagementApiControllerB
     {
         var viewModel = new TItem
         {
-            Name = entity.Name!,
             Id = entity.Key,
             Type = _itemUdiType,
             HasChildren = entity.HasChildren,
-            IsContainer = entity.IsContainer,
-            ParentId = parentKey
+            Parent = parentKey.HasValue
+                ? new ReferenceByIdModel
+                {
+                    Id = parentKey.Value
+                }
+                : null
         };
 
         return viewModel;