fix: mock http server for volcenginecr adapt ut

[hyy0322]

Thank you for contributing to Harbor!

Comprehensive Summary of your change

Issue being fixed

Fixes #22808

Please indicate you've done the following:

• Well Written Title and Summary of the PR
• Label the PR as needed. "release-note/ignore-for-release, release-note/new-feature, release-note/update, release-note/enhancement, release-note/community, release-note/breaking-change, release-note/docs, release-note/infra, release-note/deprecation"
• Accepted the DCO. Commits without the DCO will delay acceptance.
• Made sure tests are passing and test coverage is added if needed.
• Considered the docs impact and opened a new docs issue or PR with docs changes if needed in website repository.

[Copilot]

Pull request overview

This PR refactors the volcenginecr adapter unit tests to use a mock HTTP server instead of connecting to the real Volcengine registry service. This addresses issue #22808 where tests failed due to network timeouts and instability.

Changes:

• Introduced a resolveHost function variable for dependency injection to enable test mocking
• Added an HTTP test server in Test_getRealmService that mimics the bearer authentication challenge
• Modified getRealmService to use the injectable resolveHost function

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 3 comments.

File	Description
src/pkg/reg/adapter/volcenginecr/helper.go	Added resolveHost variable function for test injection and modified getRealmService to use it
src/pkg/reg/adapter/volcenginecr/helper_test.go	Added mock HTTP server setup and test infrastructure to redirect requests to the mock server

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.

[chlins]

lgtm

[wy65701436]

lgtm

[codecov]

Codecov Report

❌ Patch coverage is 75.00000% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 65.93%. Comparing base (c8c11b4) to head (26f13d4).
⚠️ Report is 664 commits behind head on main.

Files with missing lines	Patch %	Lines
src/pkg/reg/adapter/volcenginecr/helper.go	75.00%	1 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##             main   #22810       +/-   ##
===========================================
+ Coverage   45.36%   65.93%   +20.56%     
===========================================
  Files         244     1074      +830     
  Lines       13333   116415   +103082     
  Branches     2719     2937      +218     
===========================================
+ Hits         6049    76760    +70711     
- Misses       6983    35407    +28424     
- Partials      301     4248     +3947     

Flag	Coverage Δ
unittests	65.93% <75.00%> (+20.56%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
src/pkg/reg/adapter/volcenginecr/helper.go	94.28% <75.00%> (ø)

... and 988 files with indirect coverage changes

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.
• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.