Handle Webhooks from an External Service

Build a webhook handler for my app. Check my existing integrations (payment provider, auth, CMS) and set up a webhook handler for the ones that need it.

Events to handle:
[list each event type and what your app should do]

Example:
- checkout.session.completed: create subscription record in database, send welcome email
- customer.subscription.updated: update subscription status and period end date
- customer.subscription.deleted: mark subscription as canceled, send churn email

Requirements:
1. Signature verification: verify the webhook signature using the provider's secret before processing
2. Idempotency: handle duplicate webhook deliveries gracefully (don't double-process the same event)
3. Return 200 immediately, then process async (webhook providers retry on non-200 responses)
4. Log every webhook event received (event type, timestamp, success/failure)
5. Handle unknown event types gracefully (log and ignore, don't error)

Error handling:
- If processing fails after signature is verified: log the error, still return 200 (to prevent infinite retries), queue for manual review
- If signature verification fails: return 401, log the attempt

Do NOT return errors for events you don't handle. Just acknowledge them."

**Output format:** Webhook route handler with signature verification and event processing.