Added the Create client link endpoint.

Added the dagiftcard as gift card issuer.

Added new Manage order lines endpoint.

• Added support for a dedicated cancelUrl in the Payments API and Orders API. The consumer will be sent to this URL if they cancel a payment or order. If the cancelUrl is not provided, the consumer will be sent to the redirectUrlas was already the case.
• Added support for Idempotency-Key headers in the Mollie API, making API requests repeatable and idempotent within a specific timeframe. See API idempotency.