2730 rust refactor pii_filter to own crate

[lucarlig]

🔗 Related Issue

#2730 (partial close - first checklist item)

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📝 Summary

Refactored pii_filter from a module within the plugins_rust crate into a standalone workspace subcrate. This improves modularity, enables independent versioning, and simplifies the build process for the PII filter plugin.

Changes:

• Moved pii_filter module to plugins_rust/pii_filter/ as a workspace member
• Created dedicated Cargo.toml and Makefile for the subcrate
• Updated workspace-level Cargo.toml and Makefile to reference the new subcrate
• Migrated benchmarks, tests, and documentation to the subcrate directory
• Fixed deprecated method calls (trim_left_matches → trim_start_matches, trim_right_matches → trim_end_matches)
• Updated module imports and visibility modifiers for the new structure
• Updated to 2024 edition
• changed deprecated methods downcast, blackbox

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🏷️ Type of Change

• Bug fix
• Feature / Enhancement
• Refactor
• Chore (deps, CI, tooling)
• Documentation
• Other (describe below)

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🧪 Verification

Check	Command	Status
Lint suite	make lint	✅
Unit tests	make test	✅
Coverage ≥ 80%	make coverage	36%

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✅ Checklist

• Code formatted (make black isort pre-commit)
• Tests added/updated for changes
• Documentation updated (if applicable)
• No secrets or credentials committed

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📓 Notes

This PR completes the first item of issue #2730: "move pii_filter to a subcrate including fixing Makefiles etc". The subcrate now has its own build configuration and can be developed/tested independently while remaining part of the workspace.

The refactor maintains all existing functionality while improving the project structure for better maintainability and future extensibility.

Coverage for pii_filter need to be handled in a new pr for #1620 where also performance improvements can be investigated.
The integration tests was broken and needs to be rewritten using new version of pyo3 this can be done together with the second task of #2730 once the bridge is ready.

[crivetimihai]

Excellent refactoring work, @lucarlig! The workspace structuring is clean — proper metadata inheritance, backward-compatible re-export, and the PyO3 0.28 migration is consistently applied. The let-chain refactoring using Rust 2024 edition features improves readability nicely.

One question: the subcrate's Cargo.toml has crate-type = ["rlib", "cdylib"] unconditionally. The cdylib target is only needed for the standalone Python module (with extension-module feature). Does a plain cargo build without --features extension-module succeed? If not, consider making cdylib conditional on the feature flag.

Minor: small typo in the Makefile help output — trailing period and space after make dev. LGTM!

[lucarlig]

@crivetimihai thanks for review, i removed outdated/broken integration tests, there is issue #2730 for rewriting in python and this will allow me start setting up the CI as well. cleaned up unnecessary files now should be better, completely removed the no-default-feature and cdylib are not required as you suggested.

[lucarlig]

@crivetimihai should be all good now, final review and merge, I also fixed the CI.