Check Accept-Encoding quality

[martincostello]

• Do not respond with gzip if the quality of an Accept-Encoding value is zero. See Fix Accept-Encoding parsing #3492 (comment).
• Add a custom header that returns the Redoc/swagger-ui version to resolved uncovered code.

[Copilot]

Pull Request Overview

This PR enhances how Accept-Encoding quality values are handled—specifically preventing gzip when its quality is zero—and exposes the Swagger UI and ReDoc versions via custom response headers.

• Skip gzip encoding when its quality is explicitly set to zero.
• Add x-swagger-ui-version and x-redoc-version headers to responses.
• Convert a ReDoc middleware test to a parameterized theory covering various Accept-Encoding scenarios.

Reviewed Changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 2 comments.

File	Description
test/Swashbuckle.AspNetCore.IntegrationTests/ReDocIntegrationTests.cs	Converted the test to a [Theory] with multiple Accept-Encoding inputs and built a custom request message.
src/Swashbuckle.AspNetCore.SwaggerUI/SwaggerUIMiddleware.cs	Renamed cache-header method, added Swagger UI version header, and updated ETag handling.
src/Swashbuckle.AspNetCore.ReDoc/ReDocMiddleware.cs	Renamed cache-header method, added ReDoc version header, and updated ETag handling.
src/Shared/EmbeddedResourceProvider.cs	Updated IsGZipAccepted to check the Quality property before accepting gzip.

Comments suppressed due to low confidence (2)

test/Swashbuckle.AspNetCore.IntegrationTests/ReDocIntegrationTests.cs:206

• The test only asserts the status code but does not verify that the response content was correctly decompressed or matches the expected asset. Consider adding assertions to validate the response body against the original uncompressed asset.

        Assert.Equal(HttpStatusCode.OK, response.StatusCode);

test/Swashbuckle.AspNetCore.IntegrationTests/ReDocIntegrationTests.cs:197

• The empty array literal '[]' is not valid C# syntax for an empty enumerable. Consider replacing 'encodings ?? []' with 'encodings ?? Array.Empty()' to ensure compilation and clarity.

        foreach (var encoding in encodings ?? [])

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 94.28%. Comparing base (3bff9ad) to head (c1c877b).
Report is 2 commits behind head on master.

✅ All tests successful. No failed tests found.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #3493      +/-   ##
==========================================
+ Coverage   93.88%   94.28%   +0.39%     
==========================================
  Files         110      110              
  Lines        3812     3816       +4     
  Branches      724      722       -2     
==========================================
+ Hits         3579     3598      +19     
+ Misses        233      218      -15     

Flag	Coverage Δ
Linux	94.28% <100.00%> (+0.39%)	⬆️
Windows	94.28% <100.00%> (+0.39%)	⬆️
macOS	94.28% <100.00%> (+0.39%)	⬆️

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