permission-node: update policy handler to work with new auth system

Signed-off-by: Patrik Oldsberg <poldsberg@gmail.com>

docs/backend-system/building-backends/08-migrating.md

@@ -1254,7 +1254,6 @@ In order to add your own permission policy you'll need to do the following:
 
 ```ts
 import { createBackendModule } from '@backstage/backend-plugin-api';
-import { BackstageIdentityResponse } from '@backstage/plugin-auth-node';
 import {
   PolicyDecision,
   AuthorizeResult,
@@ -1262,13 +1261,14 @@ import {
 import {
   PermissionPolicy,
   PolicyQuery,
+  PolicyQueryUser,
 } from '@backstage/plugin-permission-node';
 import { policyExtensionPoint } from '@backstage/plugin-permission-node/alpha';
 
 class CustomPermissionPolicy implements PermissionPolicy {
   async handle(
     request: PolicyQuery,
-    user?: BackstageIdentityResponse,
+    user?: PolicyQueryUser,
   ): Promise<PolicyDecision> {
     // TODO: Add code here that inspects the incoming request and user, and returns AuthorizeResult.ALLOW, AuthorizeResult.DENY, or AuthorizeResult.CONDITIONAL as needed. See the docs at https://backstage.io/docs/permissions/writing-a-policy for more information