Refactoring Services (#61)

* Refactoring ViewModels into Razor Pages models

* Cleaning up Basket viewcomponent

* Refactoring services.
Fixed bug in basket item counter.

src/ApplicationCore/Interfaces/IBasketService.cs

@@ -0,0 +1,14 @@
+using System.Collections.Generic;
+using System.Threading.Tasks;
+
+namespace ApplicationCore.Interfaces
+{
+    public interface IBasketService
+    {
+        Task<int> GetBasketItemCountAsync(string userName);
+        Task TransferBasketAsync(string anonymousId, string userName);
+        Task AddItemToBasket(int basketId, int catalogItemId, decimal price, int quantity);
+        Task SetQuantities(int basketId, Dictionary<string, int> quantities);
+        Task DeleteBasketAsync(int basketId);
+    }
+}