public IHttpActionResult PutTripInPerson([FromODataUri] string key, [FromODataUri] int tripId, Trip trip)
        {
            if (!ModelState.IsValid)
            {
                return BadRequest(ModelState);
            }

            if (tripId != trip.TripId)
            {
                return BadRequest("The TripId of Trip does not match the tripId.");
            }

            var person = TripPinSvcDataSource.Instance.People.SingleOrDefault(item => item.UserName == key);
            if (person == null)
            {
                return NotFound();
            }

            var oldTrip = person.Trips.SingleOrDefault(item => item.TripId == tripId);
            if (oldTrip == null)
            {
                return NotFound();
            }

            person.Trips.Remove(oldTrip);
            person.Trips.Add(trip);
            return Updated(trip);
        }
        public IHttpActionResult PostNewTripToPerson([FromODataUri] string key, Trip trip)
        {
            if (!ModelState.IsValid)
            {
                return BadRequest(ModelState);
            }

            var person = TripPinSvcDataSource.Instance.People.SingleOrDefault(item => item.UserName == key);
            if (person == null)
            {
                return NotFound();
            }

            trip.TripId = person.Trips.Max(item => item.TripId) + 1;
            person.Trips.Add(trip);
            return Created(trip);
        }