public HttpResponseMessage PostTrackerReadingModel(TrackerReadingModel trackerReadingModel)
 {
     TrackerReadingRepository repo = new TrackerReadingRepository();
     bool ok = repo.AddReading(trackerReadingModel);
     if(ok)
         return Request.CreateResponse(HttpStatusCode.OK);
     else
     {
         return Request.CreateResponse(HttpStatusCode.BadRequest);
     }
 }