Authentication class cleanup and tests

[joshcanhelp]

Changes

Very minimal functionality changes.

• Allow null $client_id for Authentication::get_samlp_link(), Authentication::get_samlp_metadata_link(), and Authentication::get_wsfed_link() to use initialized client ID value.
• Add request parameters to Authentication::get_wsfed_link()
• Docblock improvements throughout Authentication class, along with TODOs for deprecation and exclusions from code quality scan.

Testing

• This change adds test coverage

Checklist

• All existing and new tests complete without errors.
• The correct base branch is being used.

[github-actions]

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