add support for message bulk delete
- add
POST /api/v6/channels/:id/messages/bulk-delete - make validate() raise 400 when JSON is not given
- make
LitecordErrorcheck if the first argument is an integer, and if so, checkERR_MSG_MAPfor it
POST /api/v6/channels/:id/messages/bulk-delete
LitecordError check if the first argument is an integer, and if so, check ERR_MSG_MAP for it