Send a message to one or more recipients.
Bearer authentication header of the form Bearer <token>, where <token> is your auth token.
Defines the message to be delivered
A successful call to POST /send returns a 202 status code along with a requestId in the response body.
For single-recipient requests, the requestId is the derived message_id. For multiple recipients, Courier assigns a unique message_id to each derived message.
"1-65f240a0-47a6a120c8374de9bcf9f22c"