public OperationResult <BookInfoDto> AddBooking(BookRequestDto bookRequestDto) //operation result . if data is null then not avaible. book oluşturulduğunda ekrana info sayfasını vercek
 {
     if (CarRepository.IsAvaible(bookRequestDto.carId, bookRequestDto.RentStartDate, bookRequestDto.RentEndDate))
     {
         var book = CreateBooking(bookRequestDto);
         BookRepository.AddAndSave(book);
         return(new OperationResult <BookInfoDto>(true, "Successfully booked", (int)HttpStatusCode.OK, book.ToBookInfoDto()));
     }
     else
     {
         return(new OperationResult <BookInfoDto>(false, "These dates are not available for the selected car", (int)HttpStatusCode.NotFound, null));
     }
 }