added redis integration and command line arguments handling to cart service. Didn't test in the cloud yet

src/cartservice/interfaces/ICartStore.cs

@@ -0,0 +1,12 @@
+using System.Threading.Tasks;
+
+namespace cartservice.interfaces
+{
+    internal interface ICartStore
+    {
+        Task AddItemAsync(string userId, string productId, int quantity);
+        Task EmptyCartAsync(string userId);
+
+        Task<Hipstershop.Cart> GetCartAsync(string userId);
+    }
+}