Orders with different carriers

A single order can only contain flight services from one carrier. If the flight service contains flights from different carriers, the client must split the service and send them as separate orders.

The order ID must be unique per carrier. The same order ID can be used for different carriers though.

In case there is an order existing for a flight service and the client wants to rebook the service to a different carrier, the existing order must be cancelled. Afterwards, a new order has to be created for the new carrier