chore: Clean up codebase

[kailash-b]

✏️ Changes

This PR cleans up the codebase as part of release readiness. No public behavior changes are intended; the goal is to reduce the public API surface, fix dependency versioning, and improve documentation.

Modified

• Reduced the public API surface by marking internal-only types as internal instead of public:
  • Utils
  • DPoP event handlers: ChallengeHandler, MessageReceivedHandler, TokenValidationHandler, DPoPEventHandlerBase, and IDPoPEventHandler<T>
• Pinned Microsoft.Extensions.Logging.Abstractions per target framework so each TFM resolves the matching major version (8.0.3 for net8.0, 10.0.8 for net10.0), instead of forcing 10.0.8 on both.
• README updates:
  • Moved the Security requirements section for DomainsResolver (MCD) to sit alongside the multiple custom domains configuration where it is more discoverable.
  • Added a Vulnerability Reporting section pointing to Auth0's Responsible Disclosure Program.

Removed

• Deleted the unused Auth0.AspNetCore.Authentication.Api.nuspec file (packaging is driven by the .csproj).

🔗 References

N/A — internal release-readiness cleanup.

🎯 Testing

These are non-functional changes (visibility modifiers, packaging metadata, dependency version conditions, and documentation). Existing unit tests continue to pass and the package builds against both net8.0 and net10.0. The affected types were not part of the intended public API, so no consumer-facing behavior changes.

• This change adds unit test coverage
• This change adds integration test coverage
• This change has been tested on the latest version of the platform/language or why not

✅ Checklist

• I have read the Auth0 general contribution guidelines
• I have read the Auth0 Code of Conduct
• All existing and new tests complete without errors
• All commits are signed.

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 92.53%. Comparing base (37f2e4e) to head (4c354c7).

Additional details and impacted files

@@           Coverage Diff           @@
##           master      #73   +/-   ##
=======================================
  Coverage   92.53%   92.53%           
=======================================
  Files          29       29           
  Lines        1433     1433           
  Branches      164      164           
=======================================
  Hits         1326     1326           
  Misses         76       76           
  Partials       31       31           

☔ View full report in Codecov by Harness.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.

[tanya732]

LGTM