added mongodb mvc sample

sample/MongoIdentitySample.Mvc/Models/ApplicationUser.cs

@@ -0,0 +1,9 @@
+using AspNetCore.Identity.MongoDbCore.Models;
+
+namespace MongoIdentitySample.Mvc.Models
+{
+    // Add profile data for application users by adding properties to the ApplicationUser class
+    public class ApplicationUser : MongoIdentityUser
+    {
+    }
+}