Limit allowed redirect URLs from GetAuthorizationURL

[evankanderson]

Summary

Currently, it is possible to set an arbitrary redirect URL after completing Minder login. Limit this to localhost (for CLI), or known endpoints in our config.

Change Type

Mark the type of change your PR introduces:

• Bug fix (resolves an issue without affecting existing features)
• Feature (adds new functionality without breaking changes)
• Breaking change (may impact existing functionalities or require documentation updates)
• Documentation (updates or additions to documentation)
• Refactoring or test improvements (no bug fixes or new functionality)

Testing

Added unit tests -- I'm wondering if we should put this behind a configuration option as well for easier rollback if I got something wrong.

Review Checklist:

• Reviewed my own code for quality and clarity.
• Added comments to complex or tricky code sections.
• Updated any affected documentation.
• Included tests that validate the fix or feature.
• Checked that related changes are merged.

[coveralls]

coverage: 56.595% (+0.006%) from 56.589%
when pulling 086724d on evankanderson:controlled-redirects
into 14b2907 on mindersec:main.