The following rules are applied if dialog's type is 2(GROUP):
Any user from occupants_ids can add other users.
Any user from occupants_ids can remove only himself.
Only dialog's creator(owner) can remove any users from occupants_ids.
The following rules are applied if dialog's type is 1(PUBLIC_GROUP):
Only dialog’s owner can update it.
User can update group chat dialog name, add new occupants or leave this group chat. To add more occupants use push operator. To leave group chat (remove yourself) - use pull operator: