code: private void migrateGroups(Node startNode) throws Exception
     {
        NodeIterator iterator = ((ExtendedNode)startNode).getNodesLazily();
        GroupHandlerImpl gh = ((GroupHandlerImpl)service.getGroupHandler());
        while (iterator.hasNext())
        {
           Node oldGroupNode = iterator.nextNode();
           gh.migrateGroup(oldGroupNode);
  
           migrateGroups(oldGroupNode);
        }
     }
docs: Method for groups migration.
  @throws Exception