PUT ridership/route-setups: Accept external IDs on PUT /ridership/route-setups

The PUT ridership/route-setups endpoint has some new features! routeId, passengers[].passengerId, passengers[].pickUpStopId, and passengers[].dropOffStopId now accept either a Samsara ID or an external ID in key:value format. Existing callers using numeric IDs or UUIDs are unaffected.