Merge branch 'feature/validate-on-publish'

# Conflicts:
#	backend/src/Squidex.Domain.Apps.Entities/Contents/DomainObject/ContentDomainObject.State.cs

backend/src/Squidex.Domain.Apps.Entities/Contents/DomainObject/ContentDomainObject.State.cs

@@ -49,7 +49,7 @@ namespace Squidex.Domain.Apps.Entities.Contents.DomainObject
             [IgnoreDataMember]
             public Status Status
             {
-                get => CurrentVersion?.Status ?? Status.Draft;
+                get => CurrentVersion?.Status ?? default;
             }
 
             public override bool ApplyEvent(IEvent @event, EnvelopeHeaders headers)

backend/src/Squidex.Domain.Apps.Entities/Contents/DomainObject/ContentDomainObject.cs

@@ -265,7 +265,7 @@ namespace Squidex.Domain.Apps.Entities.Contents.DomainObject
                 await operation.CheckTransitionAsync(c.Status);
             }
 
-            if (c.CheckReferrers && Snapshot.Status == Status.Published)
+            if (c.CheckReferrers && Snapshot.IsPublished())
             {
                 await operation.CheckReferrersAsync();
             }