{"agent":"claude","input":"Add Stripe Checkout to this Express app for one fixed-price product. Add POST /api/checkout, behind the existing auth.required middleware, that creates a Checkout Session for STRIPE_PRICE_ID with the user's id as client_reference_id. Add a success route that reads the Session back from Stripe. Add POST /api/checkout/webhook, registered in src/main.ts before bodyParser.json() with express.raw so the signature check sees the raw body, that verifies the Stripe-Signature header with STRIPE_WEBHOOK_SECRET and records checkout.session.completed in a new Prisma Purchase model keyed by the Session id, with a migration. Test it in the sandbox: run Postgres, start the server, forward events with stripe listen, run stripe trigger checkout.session.completed, and also send one request with a bad signature. Run npm test and nx build. Open a pull request whose description includes the stripe listen output, the trigger output and the test output.","resources":[{"url":"https://github.com/your-org/your-app"}]}