Implement Stripe mandate and mandate_data for recurring SCA compliance under EU PSD2 for subscription payments

Steps

1. When setting up a recurring payment under PSD2, create a SetupIntent or PaymentIntent with setup_future_usage='off_session' and include mandate_data describing the payment schedule (interval, amount) so the issuer can evaluate the mandate scope
2. The mandate_data.customer_acceptance object should reflect how the customer accepted the mandate: online (with IP address and user agent) or offline
3. After the SetupIntent or first PaymentIntent succeeds, Stripe generates a Mandate object linked to the PaymentMethod; retrieve and store the mandate ID
4. When creating subsequent off-session PaymentIntents, optionally pass the mandate parameter with the stored mandate ID to reference the existing mandate; some issuers and Stripe configurations require this
5. Display the mandate terms to the cardholder at checkout in a manner compliant with your local PSD2 or SCA implementation; this typically means showing the amount, frequency, and merchant name
6. Subscribe to mandate.updated webhooks to detect when a mandate becomes inactive or is revoked by the cardholder, and cancel the subscription accordingly