public Models.Customer CreateCustomer(CustomerDTO customerDTO)
        {
            var customer = new Customer
            {
                Firstname = customerDTO.Firstname,
                Lastname = customerDTO.Lastname,
                Phone = customerDTO.Phone,
                Mail = customerDTO.Mail,
                Street = customerDTO.Street,
                HouseNumber = customerDTO.HouseNumber,
                PostalCode = customerDTO.PostalCode,
                City = customerDTO.City,
                Native = customerDTO.Native,
                AmountOfFreeRides = customerDTO.AmountOfFreeRides,
            };

            return customer;
        }
        public ActionResult Edit(CustomerDTO customerDTO)
        {
            var customer = new Customer
            {
                CustomerId = customerDTO.CustomerId,
                Firstname = customerDTO.Firstname,
                Lastname = customerDTO.Lastname,
                Phone = customerDTO.Phone,
                Mail = customerDTO.Mail,
                Street = customerDTO.Street,
                HouseNumber = customerDTO.HouseNumber,
                PostalCode = customerDTO.PostalCode,
                City = customerDTO.City,
                Native = customerDTO.Native,
                AmountOfFreeRides = customerDTO.AmountOfFreeRides,
            };

            if (ModelState.IsValid)
            {
                db.Entry(customer).State = EntityState.Modified;
                db.SaveChanges();
                return RedirectToAction("Index");
            }
            return View(customerDTO);
        }