fix(storage): prevent deletion of segments in use by flags

[erka]

Add validation to segment deletion to prevent removing segments that are
referenced by flag rules or rollouts. This ensures data integrity by
checking all flags in the namespace before allowing segment deletion.

Closes #4183

[Copilot]

Pull Request Overview

This PR adds validation to prevent deletion of segments that are currently referenced by flag rules or rollouts, ensuring data integrity by checking all flags in the namespace before allowing segment deletion.

• Added validation logic to check for segment usage in flag rules and rollouts before deletion
• Enhanced error messages to specify which flag and rule/rollout number is using the segment
• Added comprehensive test coverage for various scenarios of segment usage

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
internal/storage/environments/fs/flipt/segments.go	Added validation logic to prevent deletion of segments referenced by flags
internal/storage/environments/fs/flipt/segments_test.go	Added comprehensive test cases for segment deletion validation scenarios

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[dosubot]

Related Documentation

Checked 4 published document(s). No updates required.

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[codecov]

Codecov Report

❌ Patch coverage is 84.61538% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 59.01%. Comparing base (4ab9d6b) to head (77d71a6).

Files with missing lines	Patch %	Lines
internal/storage/environments/fs/flipt/segments.go	84.61%	1 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##               v2    #4879      +/-   ##
==========================================
+ Coverage   58.98%   59.01%   +0.03%     
==========================================
  Files         135      135              
  Lines       16861    16874      +13     
==========================================
+ Hits         9945     9959      +14     
+ Misses       6235     6234       -1     
  Partials      681      681              

Flag	Coverage Δ
integrationtests	33.87% <0.00%> (-0.02%)	⬇️
unittests	49.76% <84.61%> (+0.04%)	⬆️

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