Webhook Implementation

Builds robust Stripe webhook handlers. Match the project's stack or ask users (Next.js route, Express, Supabase edge function).

Must-haves

1. Raw body for signature verification (no JSON pre-parse)
2. stripe.webhooks.constructEvent(body, sig, secret)
3. Idempotency -- dedupe by event.id (store processed IDs)
4. Return 200 fast; heavy work async
5. Handle only subscribed events; ignore rest gracefully

Core events (subscription SaaS)