Closes #13427: Public model registration (#14152)

* Initial work on #13427

* Clarify documentation

* Reference public models registry when populating models for ConfigTemplate context

netbox/core/models/files.py

@@ -44,6 +44,7 @@ class ManagedFile(SyncedDataMixin, models.Model):
     )
 
     objects = RestrictedQuerySet.as_manager()
+    _netbox_private = True
 
     class Meta:
         ordering = ('file_root', 'file_path')