Added backend skeleton, models and services

models/OrderModel.cs

@@ -0,0 +1,17 @@
+using DTO;
+
+public sealed class OrderModel {
+    public long OrderId { get; set; }
+    public string OrderDescription { get; set; }
+
+    public long CustomerId { get; set; }
+
+    public double TotalPrice { get; set; }
+
+    public OrderModel(OrderDto orderDTO) {
+        OrderId = orderDTO.OrderId;
+        OrderDescription = orderDTO.Description;
+        CustomerId = orderDTO.CustomerId;
+        TotalPrice = orderDTO.Products.Select(product => product.Price).Sum();
+    }
+}