Add a comment indicating how authorization codes/refresh tokens can be automatically invalidated when the security stamp is updated

samples/Mvc.Server/Controllers/AuthorizationController.cs

@@ -231,6 +231,9 @@ namespace Mvc.Server
                     OpenIdConnectServerDefaults.AuthenticationScheme);
 
                 // Retrieve the user profile corresponding to the authorization code/refresh token.
+                // Note: if you want to automatically invalidate the authorization code/refresh token
+                // when the user password/roles change, use the following line instead:
+                // var user = _signInManager.ValidateSecurityStampAsync(info.Principal);
                 var user = await _userManager.GetUserAsync(info.Principal);
                 if (user == null)
                 {