Integrate Checkout.com 3DS authentication flow using 3ds.enabled and configure success_url and failure_url for redirect-based challenge handling

Steps

1. When creating a payment via the Checkout.com Payments API, include the 3ds object in the request body with enabled set to true to request 3DS authentication
2. Set success_url and failure_url in the 3ds object (or at the top-level payment request depending on API version) to specify where the cardholder is redirected after the ACS challenge completes
3. If the payment response status is 'Pending' and _links contains a redirect URL, redirect the cardholder to that URL to complete the 3DS challenge with their issuer's ACS
4. After the challenge, the cardholder is redirected to your success_url or failure_url with a session_id or cko-session-id query parameter; use this to retrieve the final payment status via a GET to the Payments API
5. Check the payment's 3ds object in the retrieved response for eci, cavv, and authentication_response to confirm the authentication outcome and determine liability shift status
6. Subscribe to Checkout.com webhooks for payment_approved and payment_declined to handle async settlement notifications in addition to the redirect result