We've temporarily removed the ability to pay by card, replacing it with paying using a Duffel balance

When creating an "instant booking" order or paying for a "hold order", you have to provide payment details.

For now, we've removed the card payment method, which let you pass in a customer's credit/debit card details, which we then passed on to the airlines.

We've replaced it with paying with your Duffel balance by specifying balance. While you're building your integration in test mode, your balance is unlimited.