Identity Scaffolding creates empty Services folder 8233 (#8257)

Document fact that services are not generated when scaffolding Identity 
Fixes #8233 
[Internal review URL](https://review.docs.microsoft.com/en-us/aspnet/core/security/authentication/scaffold-identity?view=aspnetcore-2.1&branch=pr-en-us-8257&tabs=visual-studio)

aspnetcore/security/authentication/scaffold-identity.md

@@ -4,7 +4,7 @@ author: rick-anderson
 description: Learn how to scaffold Identity in an ASP.NET Core project.
 monikerRange: '>= aspnetcore-2.1'
 ms.author: riande
-ms.date: 5/16/2018
+ms.date: 08/16/2018
 uid: security/authentication/scaffold-identity
 ---
 # Scaffold Identity in ASP.NET Core projects
@@ -21,6 +21,9 @@ When the Identity scaffolder is run, a *ScaffoldingReadme.txt* file is created i
 
 We recommend using a source control system that shows file differences and allows you to back out of changes. Inspect the changes after running the Identity scaffolder.
 
+> [!NOTE]
+> Services are required when using [Two Factor Authentication](xref:security/authentication/identity-enable-qrcodes), [Account confirmation and password recovery](xref:security/authentication/accconfirm), and other security features with Identity. Services or service stubs aren't generated when scaffolding Identity. Services to enable these features must be added manually. For example, see [Require Email Confirmation](xref:security/authentication/accconfirm#require-email-confirmation).
+
 ## Scaffold identity into an empty project
 
 [!INCLUDE[](~/includes/scaffold-identity/id-scaffold-dlg.md)]