Deprecated: create the trip with POST /trips (or POST /trips/multiple with includeCompleteness: true) instead — the response includes completeness, the same result as POST /trips/{id}/completeness, evaluated against the values actually stored. This endpoint keeps working. Given a set of draft trip values, returns which user-profile and trip fields the form asks for before the trip is created. Scopes to the authenticated user unless a travelerId is included in the values.