Edit a previously sent message. The fields content, embed, allowed_mentions and flags can be edited by the original message author. Other users can only edit flags and only if they have the MANAGE_MESSAGES permission in the corresponding channel. When specifying flags, ensure to include all previously set flags/bits in addition to ones that you are modifying. Only flags documented in the table below may be modified by users (unsupported flag changes are currently ignored without error). Returns a message object. Fires a Message Update Gateway event.