Admin controller, Locations controller, requests to add available countries, request to get available countries

SchengenVisaApi/ApplicationLayer/GeneralNeededServices/IUnitOfWork.cs

@@ -0,0 +1,8 @@
+namespace ApplicationLayer.GeneralNeededServices;
+
+public interface IUnitOfWork
+{
+    /// Saves changes in data storage
+    /// <param name="cancellationToken">Cancellation Token</param>
+    Task SaveAsync(CancellationToken cancellationToken);
+}