docs(users): SAML instructions for use with Google Workspace

[cloudrootab]

Description

This shows a working example of how to connect XO SAML-plugin with Google Workspace SAML. It's a rough example, with simple screenshots. And I've mentioned the caveat that a successfull authentication points the user to the login screen. Needing to browse into the bare URL, for access into the dahsboard. But at least it works!

Checklist

• Commit

  • Title follows commit conventions

• Changelog

  • If visible by XOA users, add changelog entry
  • Update "Packages to release" in CHANGELOG.unreleased.md

• PR

  • If UI changes, add screenshots
  • If not finished or not tested, open as Draft

[julien-f]

Thank you for your contribution :bow: