Split tests into individual files

[Xarthisius]

This pull request adds a comprehensive suite of unit and integration tests for the tro_utils package, focusing on its models and core functionality. It introduces shared fixtures and helper functions to streamline test setup, and covers serialization, deserialization, and behavior of key classes such as ArtifactArrangement, ArtifactComposition, ArtifactLocation, CompositionFingerprint, and HashValue. The tests ensure correct handling of extra vocabulary in JSON-LD contexts, artifact deduplication, fingerprinting, and roundtrip consistency.

Key changes include:

Test Infrastructure and Shared Utilities

• Added shared fixtures in conftest.py for setting up temporary workspaces, GPG environments, and test profiles, enabling consistent and isolated test environments.
• Introduced a helper function in helpers.py to create TRO objects with GPG configuration, simplifying cryptographic test setup.

Model Unit Tests

• Added unit tests for ArtifactArrangement, verifying directory scanning, deduplication, snapshotting, and integration with TransparentResearchObject.
• Added unit tests for ArtifactComposition, covering artifact addition, fingerprinting, and retrieval by hash or ID.
• Added unit tests for ArtifactLocation, focusing on JSON-LD serialization and deserialization.
• Added unit tests for CompositionFingerprint, ensuring deterministic computation and JSON-LD roundtrips.
• Added unit tests for HashValue, testing parsing, serialization, legacy support, and equality.

Extra Context and JSON-LD Handling

• Implemented tests for handling extra vocabulary in the @context of JSON-LD, including propagation, roundtrip persistence, and extension through the TRO facade.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 95.05%. Comparing base (567c995) to head (db5c15d).
⚠️ Report is 2 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #28      +/-   ##
==========================================
+ Coverage   94.86%   95.05%   +0.19%     
==========================================
  Files          15       15              
  Lines        1051     1051              
==========================================
+ Hits          997      999       +2     
+ Misses         54       52       -2     

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