docs: def assign_document_controls_default_trigger(plpy, td):
      """Trigger to fill in document_controls when legacy publishes.
  
      A compatibilty trigger to fill in ``uuid`` and ``licenseid`` columns
      of the ``document_controls`` table that are not
      populated when inserting publications from legacy.
  
      This uuid default is not on ``modules.uuid`` column itself,
      because the value needs to be loosely associated
      with the ``document_controls`` entry
      to prevent uuid collisions and bridge the pending publications gap.
      """
      modified_state = "OK"
      uuid = td['new']['uuid']
  
      # Only do the procedure if this is a legacy publication.
      if uuid is None:
          modified_state = "MODIFY"
          plan = plpy.prepare("""\
  INSERT INTO document_controls (uuid, licenseid) VALUES (DEFAULT, $1)
  RETURNING uuid""", ('integer',))
          uuid_ = plpy.execute(plan, (td['new']['licenseid'],))[0]['uuid']
          td['new']['uuid'] = uuid_
  
      return modified_state