Address remaining usage of the old data interface

data/registry_model/datatypes.py

@@ -47,6 +47,15 @@ class RepositoryReference(datatype('Repository', [])):
 
     return model.repository.is_repository_public(self._repository_obj)
 
+  @property
+  def trust_enabled(self):
+    """ Returns whether trust is enabled in this repository. """
+    repository = self._repository_obj
+    if repository is None:
+      return None
+
+    return repository.trust_enabled
+
   @property
   def id(self):
     """ Returns the database ID of the repository. """