Mediatr example (#325)

* Updates based on documentation

* Getting the build passing

* Getting app functioning

* A few cleanups to confirm it's working as expected

* Fixing functional tests

* Updating dockerfile for 3.0

* Functional Tests now run sequentially

* Updating to latest version of moq

* Adding migration for post 3.0 upgrades

* Removing commented out lines

* Moving address and catalogitemordered configuration in to classes that own them

* Installing MediatR nuget packages

* Configure MediatR in Startup

* Creating GetMyOrders MediatR query and handler

* Adding GetOrderDetails MediatR handler

* Refactoring out default values

* Added tests for GetOrderDetails mediator handler

* Defaulting values on Models for now

* Removing some spaces

* Splitting files

* Splitting out the GetOrderDetails files

* Adding test for GetMyOrders

* restructuing folders

* Using constant

src/Web/Features/OrderDetails/GetOrderDetailsHandler.cs

@@ -0,0 +1,47 @@
+using MediatR;
+using Microsoft.eShopWeb.ApplicationCore.Interfaces;
+using Microsoft.eShopWeb.ApplicationCore.Specifications;
+using Microsoft.eShopWeb.Web.ViewModels;
+using System.Linq;
+using System.Threading;
+using System.Threading.Tasks;
+
+namespace Microsoft.eShopWeb.Web.Features.OrderDetails
+{
+    public class GetOrderDetailsHandler : IRequestHandler<GetOrderDetails, OrderViewModel>
+    {
+        private readonly IOrderRepository _orderRepository;
+
+        public GetOrderDetailsHandler(IOrderRepository orderRepository)
+        {
+            _orderRepository = orderRepository;
+        }
+
+        public async Task<OrderViewModel> Handle(GetOrderDetails request, CancellationToken cancellationToken)
+        {
+            var customerOrders = await _orderRepository.ListAsync(new CustomerOrdersWithItemsSpecification(request.UserName));
+            var order = customerOrders.FirstOrDefault(o => o.Id == request.OrderId);
+
+            if (order == null)
+            {
+                return null;
+            }
+
+            return new OrderViewModel
+            {
+                OrderDate = order.OrderDate,
+                OrderItems = order.OrderItems.Select(oi => new OrderItemViewModel
+                {
+                    PictureUrl = oi.ItemOrdered.PictureUri,
+                    ProductId = oi.ItemOrdered.CatalogItemId,
+                    ProductName = oi.ItemOrdered.ProductName,
+                    UnitPrice = oi.UnitPrice,
+                    Units = oi.Units
+                }).ToList(),
+                OrderNumber = order.Id,
+                ShippingAddress = order.ShipToAddress,
+                Total = order.Total()
+            };
+        }
+    }
+}