Include destination id in per diem response payload

It would be helpful if response payloads for the per diem api https://open.gsa.gov/api/perdiem/ included the destination id.

It is included in responses to
https://api.gsa.gov/travel/perdiem/v2/rates/conus/lodging/{year},
but not present in
https://api.gsa.gov/travel/perdiem/v2/rates/city/{city}/state/{ST}/year/{year}
https://api.gsa.gov/travel/perdiem/v2/rates/state/{ST}/year/{year}
https://api.gsa.gov/travel/perdiem/v2/rates/zip/{zip}/year/{year}