AddonSelection

Complete desired addon slugs. Omit to preserve the selection, or send [] to clear it. New quotes and direct bookings start without addons. Cannot be combined with quote_id when creating a booking (400). Booking addon edits update the existing quote in place, preserving its ID and retained addon prices. Invalid or unavailable additions reject the request without partial changes. A later booking-creation admission or payment failure follows the existing failed-booking lifecycle.