added basic repressentation of related_fields to city_serializer
added basic repressentation of related_fields to city_serializer

openaid-IATI/OIPA,openaid-IATI/OIPA,zimmerman-zimmerman/OIPA,openaid-IATI/OIPA,tokatikato/OIPA,tokatikato/OIPA,openaid-IATI/OIPA,zimmerman-zimmerman/OIPA,bryanph/OIPA,zimmerman-zimmerman/OIPA,openaid-IATI/OIPA,tokatikato/OIPA,bryanph/OIPA,bryanph/OIPA,zimmerman-zimmerman/OIPA,bryanph/OIPA,tokatikato/OIPA,zimmerman-zimmerman/OIPA