use stringifyEntityRef to build the user reference

Signed-off-by: Marco Crivellaro <marco.crive@gmail.com>

contrib/docs/tutorials/aws-alb-aad-oidc-auth.md

@@ -109,6 +109,10 @@ import {
   createRouter,
   createAwsAlbProvider,
 } from '@backstage/plugin-auth-backend';
+import {
+  DEFAULT_NAMESPACE,
+  stringifyEntityRef,
+} from '@backstage/catalog-model';
 import { Router } from 'express';
 import { PluginEnvironment } from '../types';
 
@@ -154,7 +158,7 @@ export default async function createPlugin({
             const [id] = email?.split('@') ?? '';
             // Fetch from an external system that returns entity claims like:
             // ['user:default/breanna.davison', ...]
-            const userEntityRef = `user:default/${id}`;
+            const userEntityRef = stringifyEntityRef({ kind: 'User', namespace: DEFAULT_NAMESPACE, name: id });
 
             // Resolve group membership from the Backstage catalog
             const fullEnt =