Keep transaction cleanup independent of request cancellation

[mikaelweave]

Summary

• We want to try to commit the current transaction during the exception flow in MergeInternalAsync and not let a cancellation exception bubble up an unhandled exception.
• Discussed with @SergeyGaluzo
• This is an edge case that can raise an error of trying to use an already closed transaction - see attached WI.

Changes

• SqlServerFhirDataStore.cs: pass CancellationToken.None to MergeResourcesCommitTransactionAsync in the MergeInternalAsync single-transaction catch block.
• Catch request cancellation during the retriable failure logging/delay block, fall through to failed transaction cleanup, then rethrow cancellation after cleanup.
• This prevents an already-cancelled request token from skipping server-side transaction failure marking..

AB#188321

Testing

• dotnet test src\Microsoft.Health.Fhir.SqlServer.UnitTests\Microsoft.Health.Fhir.SqlServer.UnitTests.csproj --no-restore --verbosity minimal
• dotnet build src\Microsoft.Health.Fhir.SqlServer\Microsoft.Health.Fhir.SqlServer.csproj --no-restore --nologo --verbosity quiet
• git diff --check

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 77.31%. Comparing base (b696902) to head (6bd20df).
⚠️ Report is 9 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #5574      +/-   ##
==========================================
- Coverage   77.37%   77.31%   -0.06%     
==========================================
  Files         993      996       +3     
  Lines       36418    36539     +121     
  Branches     5518     5539      +21     
==========================================
+ Hits        28177    28251      +74     
- Misses       6880     6918      +38     
- Partials     1361     1370       +9     

see 27 files with indirect coverage changes

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.
• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.