Fax Events

Receive `FAX.STATUS` lifecycle updates, including cancellation, and `FAX.RECEIVED` notifications for completed inbound faxes. Fax and these events are available only in Pinnacle's HIPAA cell. Delivery is at least once. Verify `PINNACLE-SIGNING-SECRET`, return HTTP 200 to acknowledge receipt, and deduplicate retries using the stable event `id`. Do not assume webhook delivery order; fetch `GET /fax/{id}` when you need the latest state. Fetch the same endpoint for a one-hour signed document URL; webhook payloads never contain document URLs.