Extend PVCAction itemblock plugin to support grouping PVCs under VGS label key

[shubham-pampattiwar]

Thank you for contributing to Velero!

Please add a summary of your change

• Adds support in GetRelatedItems for grouping PVCs using the VGS label key provided.
• Related PVCs in the same VGS group are included in the ItemBlock to ensure atomic snapshot coverage.

Does your change fix a particular issue?

Fixes #8935

Related to sub-task of #8865

Depends on merging #8938

Please indicate you've done the following:

• Accepted the DCO. Commits without the DCO will delay acceptance.
• Created a changelog file (make new-changelog) or comment /kind changelog-not-required on this PR.
• Updated the corresponding documentation in site/content/docs/main.

[codecov]

Codecov Report

Attention: Patch coverage is 85.10638% with 7 lines in your changes missing coverage. Please review.

Project coverage is 59.84%. Comparing base (41a6922) to head (97a4d62).
Report is 9 commits behind head on main.

Files with missing lines	Patch %	Lines
pkg/itemblock/actions/pvc_action.go	84.44%	5 Missing and 2 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #8944      +/-   ##
==========================================
+ Coverage   59.81%   59.84%   +0.02%     
==========================================
  Files         375      375              
  Lines       41056    41100      +44     
==========================================
+ Hits        24557    24595      +38     
- Misses      15010    15014       +4     
- Partials     1489     1491       +2     

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[kaovilai]

Code Review Summary ✅

Great work on implementing VGS support in the PVC ItemBlockAction plugin! This is a solid implementation that addresses issue #8935 requirements.

Overall Assessment:

• ✅ Clean implementation with proper separation of concerns
• ✅ Excellent test coverage covering edge cases
• ✅ Good error handling and logging
• ✅ Bug fix included (method name correction)
• ✅ Efficient Kubernetes client usage

Key Strengths:

1. Namespace scoping: Correctly limits PVC search to the same namespace
2. Label-based grouping: Uses efficient MatchingLabels client filtering
3. Self-exclusion: Properly excludes the current PVC from grouped results
4. Graceful degradation: Handles missing VGS configuration cleanly

Minor Enhancement Opportunities (within PR scope):

I've added specific code review comments for:

• Empty group value validation
• Enhanced error context for debugging
• Performance optimizations (early returns, pre-allocated slices)

Test Coverage:

The test suite is comprehensive. Consider adding one more edge case for empty group values to complete the coverage.

Looking forward to seeing this land! 🚀

[shubham-pampattiwar]

@sseago Addressed #8938 (review) in this PR !

[kaovilai]

LGTM!

[shubham-pampattiwar]

@Lyndon-Li @blackpiglet @kaovilai PR review request !