Spree Payments

Before writing code

Fetch live docs:

1. Fetch https://spreecommerce.org/docs/developer/core-concepts/payments for the Payment + PaymentSession model.
2. Fetch the integration repo README — https://github.com/spree/spree_stripe / spree_adyen / spree_paypal_checkout — for current install + config.
3. Check the gateway's own SDK docs (Stripe / Adyen / PayPal) for the latest API version.
4. Inspect the live Spree::Payment source for state transitions and column names.
5. Check the v5.4 announcement for the PaymentSession introduction.

Conceptual Architecture

PaymentMethod, Payment, PaymentSession