Symphony Update an existing message.

Update an existing message. The existing message must be a valid social message, that has not been deleted. The message can be provided as MessageMLV2 or PresentationML. Both formats support Freemarker templates. The optional parameter "data" can be used to provide a JSON payload containing entity data. If the message contains explicit references to entity data (in "data-entity-id" element attributes), this parameter is required. Regarding authentication, you must either use the sessionTok...