Attempting to inject a canned response into an active chat session using the Genesys Cloud Conversations API. The standard message send endpoint requires a full user object, which complicates automated injection from a backend service. Is there a specific sub-resource or flag in the POST /api/v2/conversations/messages call that allows sending a pre-defined canned response without constructing the full user payload? Current attempts return a 400 Bad Request due to missing user identifiers.