fix: do not fail builds when build-step span purge cannot find span

[Flamki]

What problem does this solve?

Fixes build failures reported in #994 when OpenTelemetry cannot find a build-step span to purge (for example with promoted-builds/freestyle execution paths).

Before this change, OtelTraceService.removeBuildStepSpan(...) threw IllegalStateException unconditionally when the span action was missing. That exception propagates from MonitoringBuildStepListener.finished(...) and can mark the build as failed.

What changed?

• Updated OtelTraceService.removeBuildStepSpan(...) to:
  • treat invalid spans as recoverable,
  • log a warning instead of throwing when STRICT_MODE is disabled (default runtime behavior),
  • preserve strict fail-fast behavior when STRICT_MODE is enabled (test/debug mode).
• Reused the same invalid-span rule for pipeline span purge path for consistency.
• Added regression tests in OtelTraceServiceTest for:
  • missing valid span + strict mode OFF => no throw,
  • missing valid span + strict mode ON => throws,
  • missing invalid span + strict mode ON => no throw.

How to test

./mvnw spotless:check
./mvnw -Dtest=OtelTraceServiceTest test

Both commands pass locally.

Breaking changes

None.

Notes

• Related to Incompatibility with promoted-builds-plugin (or jobs of type freestyle?) #994.
• Metrics report when the OpenTelemetry URL is not configured #1088 appears to be fixed upstream via opentelemetry-api-plugin PR Add more attributes to the runs #45 and dependency 1.49.0.99.vd48c9e6c4fa_b_, but the issue remains open administratively.

[ArpanC6]

Great fix @Flamki! This addresses a real pain point for users running
promoted-builds or freestyle jobs with OpenTelemetry.

A few observations after reviewing the changes:

1. STRICT_MODE approach — The dual behavior (warn vs throw) based on
   STRICT_MODE is a clean pattern. It preserves backward compatibility for
   production while keeping strict validation available for testing/debugging.

2. Test coverage — The 3 regression tests cover the key scenarios well:

   • Missing span + STRICT_MODE OFF → no throw
   • Missing span + STRICT_MODE ON → throws
   • Invalid span + STRICT_MODE ON → no throw

3. Code Coverage improvement — +8.10% line coverage and +6.48% branch
   coverage is a significant improvement alongside the fix.

4. One suggestion — Would it be worth adding a log message at FINE
   level (in addition to the WARNING) when a span is not found in non-strict
   mode? This could help with debugging in production without being too noisy.

All CI checks passing. This looks ready for review!

[Flamki]

Thanks for the suggestion and review.

I’ve implemented it in commit f1bc1dc: in non-strict mode, we now log at FINE in addition to the existing WARNING when a span cannot be found during purge. I applied this in both relevant purge paths in OtelTraceService, with no behavioral changes beyond logging.

I also re-ran ./mvnw "-Dtest=OtelTraceServiceTest" test and it passed.

[ArpanC6]

Great update @Flamki! Adding the FINE-level log alongside the existing
WARNING is exactly the right approach — it gives operators
debug-level visibility without adding noise in production.
Tests passing too.