{"agent":"claude","input":"Add Stripe Checkout to this Rails app for one fixed-price product. Add the stripe gem, a CheckoutsController (new, create, show) behind the existing Authentication concern that creates a Checkout Session for STRIPE_PRICE_ID with the current user's id as client_reference_id, and a success page that reads the Session back from Stripe. Add a Webhooks::StripeController at POST /webhooks/stripe that uses allow_unauthenticated_access, skips forgery protection on that controller only, reads the raw body with the RawRequestBody concern, verifies the Stripe-Signature header with STRIPE_WEBHOOK_SECRET, and records checkout.session.completed in a new Purchase model with a unique index on the Session id. Test it in the sandbox with stripe listen and stripe trigger checkout.session.completed, and send one request with a bad signature. Add Minitest tests, run bin/rails test, bin/rubocop and bin/brakeman, and open a pull request with the stripe listen, trigger and test output in its description.","resources":[{"url":"https://github.com/your-org/your-app"}]}