Add a controler for "User" (add and authenticate)

Back/skydiveLogs-api.Business/Interface/IUserService.cs

@@ -0,0 +1,11 @@
+using skydiveLogs_api.Model;
+
+namespace skydiveLogs_api.Business.Interface
+{
+    public interface IUserService
+    {
+        User GetByLogin(string login, string password);
+
+        void AddNewUser(User user);
+    }
+}