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/GetOrderDetails.cs

@@ -0,0 +1,17 @@
+using MediatR;
+using Microsoft.eShopWeb.Web.ViewModels;
+
+namespace Microsoft.eShopWeb.Web.Features.OrderDetails
+{
+    public class GetOrderDetails : IRequest<OrderViewModel>
+    {
+        public string UserName { get; set; }
+        public int OrderId { get; set; }
+
+        public GetOrderDetails(string userName, int orderId)
+        {
+            UserName = userName;
+            OrderId = orderId;
+        }
+    }
+}