Retrieve the webhook delivery log for an SMS conversation, including the payload, URL, response codes, and timing.
null if no webhook has been sent.sent_at — ISO timestamp of the delivery attemptresponse_code — HTTP status code returned by your endpoint, or null if the request failedresponse_time — how long the request tooksend_type — delivery method (e.g. "spawn")error_message — error details if the delivery failednull on success, or a list of error objects if a failure occurred.