[WIP] Support for specific hasher for API Keys (API_KEY_HASHERS)

[Copilot]

• Create a utility function to get the hashers setting that prioritizes API_KEY_HASHERS over PASSWORD_HASHERS
• Modify generate_key() to use the new utility function for hashing
• Modify check_apikey() to use the new utility function for password verification
• Add tests to ensure the new functionality works correctly
• Update README to document the new API_KEY_HASHERS setting
• Verify backward compatibility is maintained

Fixes #39.

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[Copilot]

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 94.73%. Comparing base (5742b9a) to head (b96af12).
Report is 7 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main      #47   +/-   ##
=======================================
  Coverage   94.73%   94.73%           
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  Files          11       11           
  Lines         266      266           
=======================================
  Hits          252      252           
  Misses         14       14           

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