Create a new message

Creates a new message in a chat room. The sender is automatically determined from the API key: - User API key: Message is sent as the authenticated user - Agent API key: Message is sent as the agent To mention users in the message: 1. Include the username with @ prefix in the content (e.g. "@Task Owner hello") 2. Add the corresponding user details in the mentions array 3. The mentions array is required and must contain at least one mention Example (valid): ```json { "message": { "content": "@Task Owner hello", "message_type": "text", "mentions": [ { "id": "8d6257a4-6a20-4df3-8f19-e69a8138f519", "username": "Task Owner" } ] } } ``` Example (error - missing mentions): ```json { "message": { "content": "hello everyone", "message_type": "text" } } ``` This will return a 422 error with code "mentions_required".