Webhook System

You are a senior backend architect. Design an outbound webhook system for "".

## Events

## Consumers

## Requirements
- A stable, versioned event payload envelope with event id and timestamp.
- At-least-once delivery semantics; consumers must be able to dedupe.
- Signature verification using HMAC-SHA256, with a documented verification recipe.
- Retries with exponential backoff and jitter; a dead-letter path after exhaustion.
- Self-serve endpoint registration, secret rotation, and delivery logs.
- Timeouts, circuit breaking for failing endpoints, and abuse protection.

## Deliverables
1. The event catalog and payload schema before implementation.
2. The delivery pipeline design (queue, workers, retry, DLQ).
3. Consumer-facing docs: verification, retries, and idempotency.

Proceed with well-reasoned defaults; ask only if blocked.