Webhook delivery ID (dedup key)

Problem Statement Sentry integrations retry webhooks on server errors or on timeouts. However, it might happen that the destination has actually processed the webhook and handled it even though Sentry marked it as failed (e.g. the destination server is having a spike in response times, Sentry request times out after 1 second but the webhook was handled). I learned that Sentry does not attach any stable ID for webhook delivery dedup (Request-Id is different on every delivery attempt of the same event). Because of this limitation, it's not always possible to build idempotent solutions. While it's not a problem for "issue created" event (we can dedup by event type and issue ID), it is a problem for "issue resolved" because it can be unresolved and solved by the same actor. Solution Brainstorm Inspiration from other services delivering webhooks: • In Stripe, each event has an unique ID, it's included in the webhook body. • In GitHub, w…