[DOC] - Add docs explaning how to configure Identity Provider Redirector

[viniciusdc]

Preliminary Checks

• This issue is not a question, feature request, RFC, or anything other than a bug report. Please post those things in GitHub Discussions: https://github.com/nebari-dev/nebari/discussions

Summary

Detailed guidance on configuring the Identity Provider Redirector feature on Keycloak for enabling and disabling the redirect to IDP login flow (as well as hiding the password based login flow)password-based

Steps to Resolve this Issue

1. Write docs

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