Hey folks.
We are implementing file uploads in our custom C# Web Messaging backend using the Guest API. The docs show the endpoint for sending messages, but I can’t find clear specs on accepted MIME types or the hard size limit for attachments.
When I try to send a 5MB PDF as a message, I get a 400 Bad Request with "error": "Invalid attachment size".
Is there a specific header or payload structure I’m missing? Or is the limit just under 5MB?