Delivery reports

An HTTP 200 means Taysend accepted the send, not that it was delivered. Terminal states come from delivery reports (or the TEST sandbox).

GET /v1/messages/:id to poll. Subscribe to message.delivered / message.failed / message.expired / message.rejected for push.

+233200000005 delivers after a delay. +233200000006 times out and is UNSAFE_TO_RETRY — Taysend will not failover that attempt.