Consolidate ArtifactDescriptorReaderDelegate into DefaultArtifactDescriptorReader

[gnodet]

Summary

This PR consolidates the ArtifactDescriptorReaderDelegate functionality directly into DefaultArtifactDescriptorReader in the main implementation (impl/maven-impl), while preserving the original delegate pattern in the deprecated compat module for backward compatibility.

Background

The ArtifactDescriptorReaderDelegate class was marked as "work in progress" and could be "changed or removed without notice" since version 3.2.4. The current implementation uses a delegate pattern with an unused extension mechanism through session config properties that appears to have no practical usage.

Changes Made

Main Implementation (impl/maven-impl)

• Consolidated functionality: Moved all methods from ArtifactDescriptorReaderDelegate as private methods in DefaultArtifactDescriptorReader
• Removed delegate pattern: Eliminated the delegate field and its initialization
• Simplified extension mechanism: Removed the unused session config properties lookup for custom delegates
• Maintained functionality: All existing behavior is preserved for normal usage
• Deleted: ArtifactDescriptorReaderDelegate.java

Compat Module (unchanged)

• Preserved original pattern: The deprecated compat module retains the original delegate pattern
• Backward compatibility: Existing code using the compat module continues to work
• Deprecation path: Since the compat module is already deprecated for removal in 4.0.0, this provides a clean migration path

Benefits

1. Cleaner codebase: Removes unnecessary abstraction that was marked as work-in-progress
2. Better encapsulation: Conversion methods are now private implementation details
3. Simplified maintenance: Fewer classes to maintain in the main implementation
4. Preserved compatibility: No breaking changes for normal usage
5. Clear migration path: Users can migrate from compat to main implementation when ready

Backward Compatibility

This change maintains backward compatibility for normal usage:

• The public API of DefaultArtifactDescriptorReader remains unchanged
• All functionality is identical, just moved from a separate class to private methods
• The only potential breaking change is for code using the undocumented extension mechanism through session config properties, which appears to be unused

Future Extension Points

If a proper extension point is needed in the future, it can be designed more explicitly with:

• Proper interfaces and contracts
• Clear documentation
• Well-defined extension mechanisms
• Proper testing and validation

This consolidation removes the work-in-progress delegate pattern and provides a cleaner foundation for any future extension needs.

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Pull Request opened by Augment Code with guidance from the PR author

[gnodet]

@elharo another look ?