{ "product_id": "scenario_abc123", "product_type": "scenario", "email": "customer@example.com", "success_url": "https://yourapp.com/success", "cancel_url": "https://yourapp.com/cancel" }
{ "checkout_url": "https://checkout.stripe.com/c/pay/...", "session_id": "cs_xxx" }
Create a Stripe checkout session for scenario/collection purchase