File upload MIME validation in Web Messaging Guest API

Can anyone clarify how to handle file uploads from customers in Web Messaging - accepted MIME types and size limits

  • Using the Guest API to post media attachments for tracing purposes
  • Sending a PNG file via PUT /api/v2/guests/media/attachments/{id}
  • Receiving a 415 Unsupported Media Type error despite correct headers
  • Need to know the exact MIME whitelist enforced by the platform
  • Also unsure if the 25MB limit applies to the raw payload or base64 encoded size