This API Endpoint makes a POST request to the Travu API in other to make an itinerary selection request based on the selected option from the customer. itinerary get stale fairly quickly, and when they do, you are no longer able to book them. Once a customer has picked an itinerary that works for them, you should retrieve the itinerary to get the most up to date version. You should do this when the customer picks an itinerary before you ask for his full passenger details and payment information.
To get the latest version of the offer, you can use the itinerary with the "Flight Select" endpoint: