Enforcing IAggregateRoot (#273)

- Enforcing it on the Async and EfRepositories
- Making CatalogBrand, Item, and Type AggregateRoots because they are
just lookup tables

src/ApplicationCore/Entities/CatalogBrand.cs

@@ -1,6 +1,8 @@
-namespace Microsoft.eShopWeb.ApplicationCore.Entities
+using Microsoft.eShopWeb.ApplicationCore.Interfaces;
+
+namespace Microsoft.eShopWeb.ApplicationCore.Entities
 {
-    public class CatalogBrand : BaseEntity
+    public class CatalogBrand : BaseEntity, IAggregateRoot
     {
         public string Brand { get; set; }
     }

src/ApplicationCore/Entities/CatalogItem.cs

@@ -1,6 +1,8 @@
-namespace Microsoft.eShopWeb.ApplicationCore.Entities
+using Microsoft.eShopWeb.ApplicationCore.Interfaces;
+
+namespace Microsoft.eShopWeb.ApplicationCore.Entities
 {
-    public class CatalogItem : BaseEntity
+    public class CatalogItem : BaseEntity, IAggregateRoot
     {
         public string Name { get; set; }
         public string Description { get; set; }

src/ApplicationCore/Entities/CatalogType.cs

@@ -1,6 +1,8 @@
-namespace Microsoft.eShopWeb.ApplicationCore.Entities
+using Microsoft.eShopWeb.ApplicationCore.Interfaces;
+
+namespace Microsoft.eShopWeb.ApplicationCore.Entities
 {
-    public class CatalogType : BaseEntity
+    public class CatalogType : BaseEntity, IAggregateRoot
     {
         public string Type { get; set; }
     }