public async Task <IActionResult> Edit(Guid id, [Bind("OutboundFlightId,CustomerId,OutboundDate,OneWay,ReturnFlightId,ReturnDate")] Travel travel)
        {
            if (id != travel.OutboundFlightId)
            {
                return(NotFound());
            }

            if (ModelState.IsValid)
            {
                try
                {
                    _context.Update(travel);
                    await _context.SaveChangesAsync();
                }
                catch (DbUpdateConcurrencyException)
                {
                    if (!TravelExists(travel.OutboundFlightId))
                    {
                        return(NotFound());
                    }
                    else
                    {
                        throw;
                    }
                }
                return(RedirectToAction(nameof(Index)));
            }
            ViewData["CustomerId"] = new SelectList(_context.Customers, "CustomerId", "CustomerId", travel.CustomerId);
            return(View(travel));
        }