Fix transaction heartbeat watchdog correlation

[mikaelweave]

ADO 192126.

Why

SQL merge transaction heartbeat bookkeeping was tied to the inbound request cancellation token. If the client canceled after a transaction row was created, heartbeat updates could stop while the server-side row still needed cleanup, leaving watchdog activity harder to correlate back to the originating batch or transaction request.

Approach

• Use a non-request cancellation token for merge transaction heartbeat updates after transaction creation.
• Store bounded request context in dbo.Transactions.Definition for schema V114+ and gate the SQL parameter for rolling upgrade compatibility.
• Return the stored context from timed-out transaction lookup and include it in watchdog cleanup telemetry when available.
• Add schema migration 114.diff.sql, update base sprocs, and bump SQL latest schema version to 114.

Notes

The stored context is intentionally bounded to the existing varchar(2000) column and excludes the full URI and query string. Older schemas do not receive @Definition, and the timeout read path tolerates missing definition columns.

Validation

• dotnet test src\Microsoft.Health.Fhir.SqlServer.UnitTests\Microsoft.Health.Fhir.SqlServer.UnitTests.csproj --no-restore --filter "FullyQualifiedName~SqlServerFhirDataStoreUnitTests|FullyQualifiedName~SqlStoreClientTests|FullyQualifiedName~TransactionWatchdogTests" --logger "console;verbosity=minimal"
• git diff --check