// POST api/reservations
 public HttpStatusCodeResult Post(Book book)
 {
     try
     {
         var user = new User()
         {
             Name = User.Identity.Name
         };
         _reservationRepo.Borrow(book, user);
         return(new HttpStatusCodeResult(200, "Book borrowed"));
     }
     catch (InvalidOperationException e)
     {
         return(new HttpStatusCodeResult(500, e.Message));
     }
 }