Creates an outbound draft to a customer through a specific channel (email, SMS, Facebook DM, etc).
sendAt property to designate a future date/time for the drafted message to be sent at.
You can also create note drafts by specifying the channel as 'note' in the request body channel field. You can have one note draft per conversation.
Customer drafts are subject to a rate limit. A single client can create up to 120 drafts per minute per customer, including drafts scheduled for the future.
429 Too Many Requests response will be returned if the rate limit has been reached for a customer.