Implement mitigation for server returning empty pages

[claucambra]

The server can return page tokens for new pages that are in fact empty given the provided token by the client. This breaks some of our assumptions.

This fixes that

[Copilot]

Pull Request Overview

This PR adds logic to stop enumeration when a server erroneously returns a next‐page token despite all items already being delivered. It includes:

• A new test testWorkingSetEnumerationStopsOnExhaustedTotal to verify the paginator halts on empty pages.
• A forceNextPageOnLastContentPage flag in MockRemoteInterface to simulate faulty servers.
• Updates in EnumeratorPageResponse, Enumerator, and the sync‐engine extension to track and apply total counts for terminating phantom pages.

Reviewed Changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
Tests/NextcloudFileProviderKitTests/EnumeratorTests.swift	Added a test verifying pagination stops when the total count is reached despite a phantom next‐page token
Tests/Interface/MockRemoteInterface.swift	Introduced forceNextPageOnLastContentPage to simulate servers that return empty pages
Sources/NextcloudFileProviderKit/Enumeration/EnumeratorPageResponse.swift	Changed total from let to var to allow updating the remaining item count on phantom pages
Sources/NextcloudFileProviderKit/Enumeration/Enumerator.swift	Added pageTotal tracking and logic to clear nextPage when index * pageItemCount >= total
Sources/NextcloudFileProviderKit/Enumeration/Enumerator+SyncEngine.swift	Modified the return for over‐indexed paginated requests to yield an empty metadata array instead of error

Comments suppressed due to low confidence (2)

Sources/NextcloudFileProviderKit/Enumeration/EnumeratorPageResponse.swift:17

• [nitpick] Update this comment to note that total may be mutated on subsequent pages (e.g., phantom pages) to control when pagination should end.

var total: Int?     // Total item count, provided in the first non-offset paginated response

Tests/NextcloudFileProviderKitTests/EnumeratorTests.swift:585

• [nitpick] The debugPrint of the database isn’t needed for this test and may clutter logs; consider removing it.

debugPrint(db)

[codecov]

Codecov Report

Attention: Patch coverage is 91.07143% with 10 lines in your changes missing coverage. Please review.

Project coverage is 84.00%. Comparing base (a869466) to head (0622638).
Report is 5 commits behind head on main.

Files with missing lines	Patch %	Lines
...tcloudFileProviderKit/Enumeration/Enumerator.swift	73.68%	5 Missing ⚠️
...roviderKit/Enumeration/Enumerator+SyncEngine.swift	0.00%	3 Missing ⚠️
Tests/Interface/MockRemoteInterface.swift	60.00%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #90      +/-   ##
==========================================
+ Coverage   83.96%   84.00%   +0.04%     
==========================================
  Files          70       70              
  Lines       15749    15852     +103     
==========================================
+ Hits        13223    13317      +94     
- Misses       2526     2535       +9     

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