post https://{tenant}.sednanetwork.com/platform/2019-01-01/message//document
Adds an attachment to a message.
Returns an S3 Upload URL that will be valid for 5 minutes. This link can be used to upload the content of the file.
If a base64 body is provided this link will already contain the content of the file.
Required API Permissions: MESSAGE_READ, MESSAGE_WRITE