Document running test suite for auth

[lukehesluke]

Ensure docs include CSS Selectors for Auth setup ✅ (#583), and explain how all test suite config for auth are used ✅

Ensure that:

• (DONE ✅ ) all auth strategies are documented, incl browser automation for auth code flow
  • Cleanup and signpost Authentication Strategies in Test Suite's docs #577
• (DONE ✅ ) auth configuration is documented, incl CSS selectors
  • They are already documented. And signposted to by Cleanup and signpost Authentication Strategies in Test Suite's docs #577
• (ISSUES ELABORATED or IN REVIEW ✅ ) openactive-openid-* packages are documented
  • config for OpenActiveTestAuthKeyManager (Document openactive-openid-test-client library AuthKeyManager config #594)
  • setupBrowserAutomationRoutes(..) (Document openactive-openid-test-client library browser automation routes #593)
  • OpenActiveOpenIdTestClient
    (Document OpenActiveOpenIdTestClient, recordWithIntercept, logWithIntercept in openactive-openid-client package #634)
• (IN REVIEW ✅ ) all references to packages/openactive-openid-test-client from this PR: docs(broker): Describe what Broker does and how to interact with it #571 are explained: Fix Broker Microservice documentation links to openactive-openid-* package docs #635
• (ISSUE ELABORATED ✅ ) it's clearly signposted to users to use the openid-test-client CLI to test their auth before running tests: Test Suite users should use openactive-openid-test-cli to verify OIDC auth before running tests developer-documentation#70

NOTE any work relating to test client are blocked until this PR is merged: #553 as it affects the structure of test client

[lukehesluke]

All issues herein have been elaborated or implemented (with some reviews pending). And therefore I will close this, which ended up being a tree node issue