ci: integrate GitHub code coverage uploads

[baywet]

Summary

• collect Cobertura coverage in the CI job
• generate a GitHub-friendly coverage summary and upload it with actions/upload-code-coverage
• publish the generated coverage report as a workflow artifact

Validation

• dotnet build Microsoft.OpenApi.slnx -c Release
• dotnet test Microsoft.OpenApi.slnx -c Release --no-build -v n --collect:"XPlat Code Coverage"
• reportgenerator -reports:**/coverage.cobertura.xml -targetdir:./reports/coverage -reporttypes:"Html;MarkdownSummaryGithub;Cobertura"

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[github-code-quality]

Code Coverage Overview

Languages: C#

C# / code-coverage/dotnet

The overall coverage in the ci/coverage-informat... branch is 42%. Coverage data for the main branch is not yet available.

Show a code coverage summary of the most covered files.

File	main	ci/coverage-informat... 2368305	+/-
/home/runner/wo...penApiSchema.cs	—	99%	—
/home/runner/wo...piComponents.cs	—	94%	—
/home/runner/wo...nApiDocument.cs	—	89%	—
/home/runner/wo...Deserializer.cs	—	87%	—
/home/runner/wo...Deserializer.cs	—	87%	—
/home/runner/wo...Deserializer.cs	—	82%	—
/home/runner/wo...Deserializer.cs	—	81%	—
/home/runner/wo...enApiService.cs	—	80%	—
/home/runner/wo...penApiWalker.cs	—	79%	—
/home/runner/wo...Deserializer.cs	—	79%	—

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_{Updated May 28, 2026 14:36 UTC
Code Coverage is in Public Preview. Learn more and provide us with your feedback.}