The above endpoint is based on the v2/payments endpoint. If you have already integrated Gateway, you can expect it to work the same way. The only difference is that you don’t need to redirect the shopper anywhere;
checkoutUrl is your payment link.
Note also that the payment link generated using pay-by-link is valid for 30 days, whereas v2/payments is for 30 minutes.
Pay by Link uses Volt’s REST API. See the authentication section here: API Reference | Volt Developer Hub.
This endpoint takes exactly the same request structure as Request payment – Request body | Volt Developer Hub. Please refer to this section of developer documentation for further information.