Add cache headers to document URLs endpoint

[Copilot]

The issue or feature being addressed

The document URLs endpoint (/swagger/documentUrls) lacks cache control headers, causing browsers to cache stale data indefinitely.

Details on the issue fix or feature implementation

Updated RespondWithDocumentUrls to compute SHA1-based ETag and apply cache headers via existing SetHeaders method, matching the pattern in RespondWithFile:

var etag = HashText(json);
SetHeaders(response, _options, etag);

Extracted HashText as a shared static method to eliminate duplication between RespondWithFile and RespondWithDocumentUrls.

Added integration test DocumentUrlsEndpoint_ReturnsJsonWithCacheHeaders verifying ETag (weak) and Cache-Control headers (Private, MaxAge=7d or no-cache/no-store based on CacheLifetime config).

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Original prompt

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This section details on the original issue you should resolve

<issue_title>[Feature request]: Cache-bust endpoint URLs resource</issue_title>
<issue_description>### Is your feature request related to a specific problem? Or an existing feature?

Context: #3709 (comment)

The document URLs endpoint can get cached in browsers and go out-of-date.

Describe the solution you'd like

We should update the method below to respond with cache headers like we do for files:

Swashbuckle.AspNetCore/src/Swashbuckle.AspNetCore.SwaggerUI/SwaggerUIMiddleware.cs

Line 180 in c2cfe84

private async Task RespondWithDocumentUrls(HttpResponse response)

Swashbuckle.AspNetCore/src/Swashbuckle.AspNetCore.SwaggerUI/SwaggerUIMiddleware.cs

Line 158 in c2cfe84

SetHeaders(response, _options, etag);

Additional context

No response</issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes [Feature request]: Cache-bust endpoint URLs resource #3710

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[Copilot]

Pull request overview

This PR ensures the Swagger UI document URLs endpoint (/swagger/documentUrls) participates in the same cache-busting behavior as other Swagger UI resources by adding ETag and cache headers. It also refactors ETag computation within SwaggerUIMiddleware to avoid duplication and adds an integration test around the new behavior.

Changes:

• Updated SwaggerUIMiddleware.RespondWithDocumentUrls to compute a SHA1-based ETag for the JSON payload and apply cache headers via the existing SetHeaders helper.
• Refactored the ETag helper from a local static function in RespondWithFile into a shared private static HashText method on SwaggerUIMiddleware.
• Added an integration test DocumentUrlsEndpoint_ReturnsJsonWithCacheHeaders to verify that /swagger/documentUrls returns the expected content type, body contents, weak ETag, and Cache-Control headers (private with 7-day max-age under default configuration).

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
src/Swashbuckle.AspNetCore.SwaggerUI/SwaggerUIMiddleware.cs	Reuses a shared HashText helper and updates RespondWithDocumentUrls to emit weak ETags and cache headers consistent with other Swagger UI responses.
test/Swashbuckle.AspNetCore.IntegrationTests/SwaggerUIIntegrationTests.cs	Adds an integration test for /swagger/documentUrls to assert content, weak ETag presence, and Cache-Control configuration under the default MultipleVersions test site setup.

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 94.90%. Comparing base (1bbe001) to head (796008d).
⚠️ Report is 1 commits behind head on master.
✅ All tests successful. No failed tests found.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #3766      +/-   ##
==========================================
+ Coverage   94.67%   94.90%   +0.23%     
==========================================
  Files         111      111              
  Lines        3868     3870       +2     
  Branches      780      780              
==========================================
+ Hits         3662     3673      +11     
+ Misses        206      197       -9     

Flag	Coverage Δ
Linux	94.90% <100.00%> (+0.23%)	⬆️
Windows	94.90% <100.00%> (+0.23%)	⬆️
macOS	94.90% <100.00%> (+0.23%)	⬆️

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