public ActionResult AddCustomerData(AddCustomerModel model)
        {
            var sessionFacade = new SessionFacade(HttpContext.Session);
            var categories = _storageContext.Categories.LoadAll();

            if (!ModelState.IsValid)
            {
                model.Categories = categories;
                return View("OrderCart", model);
            }

            // do handle customer
            var customer = new Customer
            {
                Id = model.CustomerId,
                Salutation = model.Salutation,
                Name = model.Name,
                FamilyName = model.FamilyName,
                Address = model.Address,
                Zip = model.Zip,
                City = model.City,
                Email = model.Email
            };

            sessionFacade.Customer = customer;

            return RedirectToAction("OrderReview");
        }
        public ActionResult OrderCart()
        {
            var sessionFacade = new SessionFacade(HttpContext.Session);
            var categories = _storageContext.Categories.LoadAll();

            var customer = sessionFacade.Customer;

            var model = new AddCustomerModel
            {
                Categories = categories,
                CustomerId = customer.Id,
                Name = customer.Name,
                FamilyName = customer.FamilyName,
                Address = customer.Address,
                Zip = customer.Zip,
                City = customer.City,
                Email = customer.Email
            };

            return View(model);
        }