Add Notification Service.

Author: mohammadKarimi

.vs/slnx.sqlite

@@ -0,0 +1,14 @@
+public class NotificationService
+{
+    public ... CreateNotification(string type)
+    {
+        if (type == "Email")
+            return new ...();
+        else if (type == "SMS")
+            return new ...();
+        else if (type == "Push")
+            return new ...();
+        else
+            throw new ArgumentException("Invalid notification type.");
+    }
+}