fix(files): add FsNode.etag_unquoted, keep etag as the server sent it

[oleksandr-nc]

FsNode.etag keeps what the server sent, quotes included, so it can be passed to an If-Match/If-None-Match header unchanged. Stripping them there would break that, measured against NC 35: the server answers 412 to a conditional write and silently ignores the precondition on a conditional read (200 instead of 304). The quotes are part of the entity tag (RFC 9110 §8.8.3).

• add FsNode.etag_unquoted for callers that want the bare tag, which is what Quoted E-Tags may be stripped #448 asks for
• FsNode.etag is always a str now: the trashbin sends an empty <d:getetag/>, which used to arrive as None
• 9 unit tests over every source shape, plus an integration test that sends the unmodified etag back to the server and expects 304/2xx

Closes #448

Summary by CodeRabbit

• New Features

  • Added etag_unquoted for retrieving ETags without surrounding quotation marks.
  • etag now preserves the server-provided format for direct use in conditional request headers.
  • Missing ETags consistently return as empty strings, including for trashbin entries.

• Bug Fixes

  • Standardized ETag handling across file listings, responses, and file metadata.
  • Improved coverage for quoted, unquoted, and missing ETag values.

[coderabbitai]

📝 Walkthrough

Walkthrough

FsNode.etag now preserves server-provided quotes and always returns a string. FsNode.etag_unquoted provides the quote-stripped value. Unit and integration tests cover ETag sources and conditional DAV requests.

Changes

ETag normalization

Layer / File(s)	Summary
Normalize FsNode ETags nc_py_api/files/__init__.py, CHANGELOG.md	FsNode preserves quoted ETags, converts missing or None values to "", and exposes etag_unquoted. Documentation and the changelog describe the updated behavior.
Validate ETag sources tests_unit/test_etag_normalization.py, tests/actual_tests/files_test.py	Tests cover direct construction, Propfind data, response headers, ActionFileInfo conversion, filesystem listings, and conditional DAV requests.

Estimated code review effort: 2 (Simple) | ~10 minutes

Sequence Diagram(s)

sequenceDiagram
  participant DAVServer
  participant FsNode
  participant Client
  DAVServer->>FsNode: Return server-provided quoted ETag
  FsNode->>Client: Expose etag and etag_unquoted
  Client->>DAVServer: Send quoted ETag in conditional DAV headers
  DAVServer-->>Client: Return 304 or accept conditional PUT

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🚥 Pre-merge checks | ✅ 3 | ❌ 2

❌ Failed checks (2 warnings)

Check name	Status	Explanation	Resolution
Linked Issues check	⚠️ Warning	The PR preserves quoted FsNode.etag and adds etag_unquoted, but issue #448 requests stripping quotes from the exposed ETag.	Make FsNode.etag unquoted as requested by #448, or update the issue and compatibility requirements to approve the dual-property API.
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (3 passed)

Check name	Status	Explanation
Out of Scope Changes check	✅ Passed	The code, changelog, and tests directly support ETag representation and conditional request behavior.
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly describes the main API change: adding FsNode.etag_unquoted while preserving the server-provided FsNode.etag value.

✨ Finishing Touches 💡 1

📝 Generate docstrings 💡

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch fix/etag-quotes

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 94.79%. Comparing base (126a31e) to head (9611972).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #456      +/-   ##
==========================================
+ Coverage   94.69%   94.79%   +0.10%     
==========================================
  Files          48       50       +2     
  Lines        5650     5767     +117     
==========================================
+ Hits         5350     5467     +117     
  Misses        300      300              

Files with missing lines	Coverage Δ
nc_py_api/files/__init__.py	99.72% <100.00%> (+<0.01%)	⬆️
tests_unit/test_etag_normalization.py	100.00% <100.00%> (ø)

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