Refactoring and Adding Tests (#28)

* Introducing repository and refactoring services.
Changing entities to use int keys everywhere.

* Refactoring application services to live in web project and only reference repositories, not EF contexts.

* Cleaning up implementations

* Moving logic out of CatalogController
Moving entity knowledge out of viewmodels.

* Implementing specification includes better for catalogservice

* Cleaning up and adding specification unit tests

src/ApplicationCore/Specifications/BasketWithItemsSpecification.cs

@@ -0,0 +1,28 @@
+using ApplicationCore.Interfaces;
+using Microsoft.eShopWeb.ApplicationCore.Entities;
+using System;
+using System.Linq.Expressions;
+using System.Collections.Generic;
+
+namespace ApplicationCore.Specifications
+{
+    public class BasketWithItemsSpecification : ISpecification<Basket>
+    {
+        public BasketWithItemsSpecification(int basketId)
+        {
+            BasketId = basketId;
+            AddInclude(b => b.Items);
+        }
+
+        public int BasketId { get; }
+
+        public Expression<Func<Basket, bool>> Criteria => b => b.Id == BasketId;
+
+        public List<Expression<Func<Basket, object>>> Includes { get; } = new List<Expression<Func<Basket, object>>>();
+
+        public void AddInclude(Expression<Func<Basket, object>> includeExpression)
+        {
+            Includes.Add(includeExpression);
+        }
+    }
+}