Handle user id 0 (Unknown/System) when building content version response (#19361)

Handle user id 0 (Unknown/System) when building content version response model

`IUserIdKeyResolver.GetAsync` throws an exception when a user is not found.
As user 0 does not really exist, the exception was being thrown.
We now handle this scenario to return an empty reference.

Author: lauraneto

src/Umbraco.Cms.Api.Management/Factories/DocumentVersionPresentationFactory.cs

@@ -1,5 +1,6 @@
 using Umbraco.Cms.Api.Management.ViewModels;
 using Umbraco.Cms.Api.Management.ViewModels.Document;
+using Umbraco.Cms.Core;
 using Umbraco.Cms.Core.Models;
 using Umbraco.Cms.Core.Services;
 using Umbraco.Extensions;
@@ -19,17 +20,26 @@ public DocumentVersionPresentationFactory(
         _userIdKeyResolver = userIdKeyResolver;
     }
 
-    public async Task<DocumentVersionItemResponseModel> CreateAsync(ContentVersionMeta contentVersion) =>
-        new(
+    public async Task<DocumentVersionItemResponseModel> CreateAsync(ContentVersionMeta contentVersion)
+    {
+        ReferenceByIdModel userReference = contentVersion.UserId switch
+        {
+            Constants.Security.UnknownUserId => new ReferenceByIdModel(),
+            _ => new ReferenceByIdModel(await _userIdKeyResolver.GetAsync(contentVersion.UserId)),
+        };
+
+        return new DocumentVersionItemResponseModel(
             contentVersion.VersionId.ToGuid(), // this is a magic guid since versions do not have keys in the DB
             new ReferenceByIdModel(_entityService.GetKey(contentVersion.ContentId, UmbracoObjectTypes.Document).Result),
-            new ReferenceByIdModel(_entityService.GetKey(contentVersion.ContentTypeId, UmbracoObjectTypes.DocumentType)
-                .Result),
-            new ReferenceByIdModel(await _userIdKeyResolver.GetAsync(contentVersion.UserId)),
+            new ReferenceByIdModel(
+                _entityService.GetKey(contentVersion.ContentTypeId, UmbracoObjectTypes.DocumentType)
+                    .Result),
+            userReference,
             new DateTimeOffset(contentVersion.VersionDate),
             contentVersion.CurrentPublishedVersion,
             contentVersion.CurrentDraftVersion,
             contentVersion.PreventCleanup);
+    }
 
     public async Task<IEnumerable<DocumentVersionItemResponseModel>> CreateMultipleAsync(IEnumerable<ContentVersionMeta> contentVersions)
         => await CreateMultipleImplAsync(contentVersions).ToArrayAsync();