List webhook subscriptions

Webhook subscriptions deliver reservation.created, reservation.updated, reservation.deleted, guest.created, guest.updated and guest.deleted events to your server as signed POST requests (X-Hotelumo-Signature: t=<timestamp>,v1=<hex HMAC-SHA256 of "timestamp.body">). An endpoint failing 20 times in a row is disabled automatically. Subscriptions are managed with an operator access token; the secret is only returned once, on create.