Add baggage and meal ancillaries to a Duffel order

Steps

1. After creating an offer request and selecting an offer, call GET /air/offers/{offer_id} and inspect the available_services array for services of type 'baggage' and 'meal'.
2. For baggage services, read the metadata fields for total_weight_kg and quantity to present meaningful descriptions; for meals, read the meal_code or description field.
3. Build a services array mapping each service_id to the relevant passenger_id and segment_id; include this in the order creation POST body under the services key.
4. Confirm the ancillaries were accepted by inspecting the services array on the created order response; each entry should include a confirmed_at timestamp.
5. For post-booking ancillary additions (where the airline supports it), call POST /air/orders/{id}/services with the additional service objects.
6. Surface the itemized ancillary costs in your booking summary UI, clearly separated from the base fare.