1008: Invalid iMessage app message

The imessage_app message part is invalid. This is an HTTP 400 error. The message field names the specific problem, so read it before checking anything else.

• app.name is required, and app.team_id must be 10 uppercase alphanumeric characters
• app.bundle_id is required and must not contain :
• url must be either an absolute https:// URL or a data: URL
• layout must set at least one of caption, subcaption, trailing_caption, trailing_subcaption, or image_url
• image_title and image_subtitle require image_url — an overlay needs an image to sit on
• An imessage_app part must be the only part in the message

• iMessage Apps
• API reference: Send a message
• Error Codes