Improve stability of thumbnail url generation

[claucambra]

No description provided.

[Copilot]

Pull Request Overview

This PR refactors the thumbnail URL generation to use modern URL-building APIs with availability checks and adds a unit test to validate the new logic.

• Switches from manual string concatenation to URL.appending(components:) and query items on supported OS versions.
• Provides a fallback string-based URL constructor for older OS versions.
• Introduces a unit test to verify the generated thumbnail URL.

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 3 comments.

File	Description
Tests/NextcloudFileProviderKitTests/ItemMetadataTests.swift	Adds a test (thumbnailUrlCorrect) to assert that thumbnailUrl(size:) produces the expected URL.
Sources/NextcloudFileProviderKit/Metadata/ItemMetadata.swift	Replaces legacy URL string building with appending(components:) and query items, guarded by an availability check.

Comments suppressed due to low confidence (1)

Tests/NextcloudFileProviderKitTests/ItemMetadataTests.swift:21

• Add a complementary test case for hasPreview == false (e.g. when item.hasPreview is false) to ensure thumbnailUrl(size:) correctly returns nil.

#expect(item.thumbnailUrl(size: .init(width: 250, height: 250)) == expectedUrl)

[codecov]

Codecov Report

Attention: Patch coverage is 86.95652% with 3 lines in your changes missing coverage. Please review.

Project coverage is 81.24%. Comparing base (d73df81) to head (87ff073).
Report is 8 commits behind head on main.

Files with missing lines	Patch %	Lines
...xtcloudFileProviderKit/Metadata/ItemMetadata.swift	76.92%	3 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #79      +/-   ##
==========================================
+ Coverage   81.08%   81.24%   +0.16%     
==========================================
  Files          62       63       +1     
  Lines       13505    13562      +57     
==========================================
+ Hits        10951    11019      +68     
+ Misses       2554     2543      -11     

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