♻️ remove internal Undefined sentinel references

[techouse]

This pull request makes Undefined an internal implementation detail rather than a public API, and updates documentation and tests to reflect this. It also clarifies and improves the documentation for charset sentinels and the Sentinel enum.

Public API changes:

• Removed Undefined from the public API by deleting its import and export from qs_codec/__init__.py, and removing its documentation and usage examples from the docs and README files. [1] [2] [3] [4] [5] [6]
• Added tests to ensure that Sentinel is part of the public API and Undefined is not.

Documentation improvements:

• Improved and clarified the docstrings and comments for Sentinel and _SentinelDataMixin in sentinel.py, making their roles and usage clearer and more precise. [1] [2]
• Updated the Undefined implementation and docstring to clarify its internal, singleton nature and prevent subclassing, and removed its __all__ export. [1] [2] [3]

Changelog:

• Added a changelog entry for version 1.6.0-dev documenting the removal of qs_codec.Undefined from the public API.

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ℹ️ Review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro

Run ID: ad996a6a-e1d8-4295-9e04-8d89a4702b11

📥 Commits

Reviewing files that changed from the base of the PR and between 735f05c and 8f55f8d.

📒 Files selected for processing (9)

• CHANGELOG.md
• README.rst
• docs/README.rst
• docs/qs_codec.models.rst
• src/qs_codec/__init__.py
• src/qs_codec/enums/sentinel.py
• src/qs_codec/models/undefined.py
• tests/unit/example_test.py
• tests/unit/package_test.py

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch chore/api-cleanup

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[codacy-production]

Up to standards ✅

🟢 Issues 0 issues

Results:
0 new issues

View in Codacy

🟢 Metrics 0 complexity · 0 duplication

Metric	Results
Complexity	0
Duplication	0

View in Codacy

🟢 Coverage 100.00% diff coverage · +0.00% coverage variation

Metric	Results
Coverage variation	✅ +0.00% coverage variation (-1.00%)
Diff coverage	✅ 100.00% diff coverage

View coverage diff in Codacy

Coverage variation details

	Coverable lines	Covered lines	Coverage
Common ancestor commit (735f05c)	1931	1931	100.00%
Head commit (8f55f8d)	1931 (+0)	1931 (+0)	100.00% (+0.00%)

Coverage variation is the difference between the coverage for the head and common ancestor commits of the pull request branch: <coverage of head commit> - <coverage of common ancestor commit>

Diff coverage details

	Coverable lines	Covered lines	Diff coverage
Pull request (#55)	3	3	100.00%

Diff coverage is the percentage of lines that are covered by tests out of the coverable lines that the pull request added or modified: <covered lines added or modified>/<coverable lines added or modified> * 100%

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TIP This summary will be updated as you push new changes.}

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 100.00%. Comparing base (735f05c) to head (8f55f8d).

Additional details and impacted files

@@            Coverage Diff            @@
##              main       #55   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files           22        22           
  Lines         1931      1931           
=========================================
  Hits          1931      1931           

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[Copilot]

Pull request overview

This pull request narrows the library’s public surface area by removing the Undefined sentinel from the package-root API (qs_codec.Undefined), while keeping sentinel behavior as an internal implementation detail and clarifying Sentinel documentation.

Changes:

• Removed Undefined from qs_codec/__init__.py exports and removed its usage examples and module docs from README/Sphinx docs.
• Improved docstrings for charset sentinel handling (Sentinel) and clarified Undefined as an internal singleton sentinel with no public exports.
• Added unit tests to assert Sentinel remains public and Undefined is not exported from the package root.

Reviewed changes

Copilot reviewed 9 out of 9 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
tests/unit/package_test.py	Adds assertions for public API surface (Sentinel exported; Undefined not exported).
tests/unit/example_test.py	Removes public-facing qs_codec.Undefined() example usage.
src/qs_codec/models/undefined.py	Marks Undefined as internal, removes module exports, and tightens singleton/subclassing semantics documentation.
src/qs_codec/enums/sentinel.py	Clarifies Sentinel docstrings and explicitly defines intended exports.
src/qs_codec/init.py	Removes Undefined from package-root imports and __all__.
README.rst	Removes Undefined from public documentation/examples.
docs/README.rst	Removes Undefined from public documentation/examples.
docs/qs_codec.models.rst	Removes the qs_codec.models.undefined module from generated docs.
CHANGELOG.md	Documents removal of qs_codec.Undefined from the public API in the next dev cycle.