message: Update API request auth contrib doc for 1.6, use identity from app environment.
diff: @@ -11,12 +11,8 @@ As techdocs HTML pages load assets without an Authorization header the code belo
  Create `packages/backend/src/authMiddleware.ts`:
  ```typescript
  -import { SingleHostDiscovery } from '@backstage/backend-common';
  import type { Config } from '@backstage/config';
  -import {
  - getBearerTokenFromAuthorizationHeader,
  - IdentityClient,
  -} from '@backstage/plugin-auth-node';
  +import { getBearerTokenFromAuthorizationHeader } from '@backstage/plugin-auth-node';
  import { NextFunction, Request, Response, RequestHandler } from 'express';
  import { decodeJwt } from 'jose';
  import { URL } from 'url';
  @@ -45,11 +41,6 @@ export const createAuthMiddleware = async (
  config: Config,
  appEnv: PluginEnvironment,
  ) => {
  - const discovery = SingleHostDiscovery.fromConfig(config);
  - const identity = IdentityClient.create({
  - discovery,
  - issuer: await discovery.getExternalBaseUrl('auth'),
  - });
  const baseUrl = config.getString('backend.baseUrl');
  const secure = baseUrl.startsWith('https://');
  const cookieDomain = new URL(baseUrl).hostname;
  @@ -67,7 +58,7 @@ export const createAuthMiddleware = async (
  return;
  }
  try {
  - req.user = await identity.authenticate(token);
  + req.user = await appEnv.identity.getIdentity({ request: req });
  } catch {
  await appEnv.tokenManager.authenticate(token);
  }
  