Refactor fanout exporter concurrent dispatch

[Copilot]

fanoutExporter.ExportSpans and fanoutExporter.Shutdown carried the same concurrent fan-out and error aggregation logic, differing only in the exporter method invoked. This change consolidates that shared behavior so future updates to fan-out semantics happen in one place.

• Shared dispatch path

  • Add a private forEachExporter helper on fanoutExporter
  • Preserve the existing behavior: invoke all exporters concurrently, tolerate partial failures, and return joined errors

• Public method simplification

  • Refactor ExportSpans to delegate span export through the helper
  • Refactor Shutdown to delegate exporter shutdown through the helper

• Coverage update

  • Add focused test coverage for the extracted helper to verify all exporters are visited and callback errors are propagated

func (f *fanoutExporter) ExportSpans(ctx context.Context, spans []sdktrace.ReadOnlySpan) error {
	return f.forEachExporter(func(e sdktrace.SpanExporter) error {
		return e.ExportSpans(ctx, spans)
	})
}

func (f *fanoutExporter) Shutdown(ctx context.Context) error {
	return f.forEachExporter(func(e sdktrace.SpanExporter) error {
		return e.Shutdown(ctx)
	})
}

[Copilot]

Pull request overview

This PR refactors the tracing fanout span exporter to centralize its concurrent fan-out and error aggregation behavior into a single private helper, reducing duplication between ExportSpans and Shutdown while preserving existing semantics.

Changes:

• Extract shared concurrent dispatch + joined-error aggregation into (*fanoutExporter).forEachExporter.
• Refactor ExportSpans and Shutdown to delegate to the shared helper.
• Add a focused unit test validating that the helper visits all exporters and propagates callback errors.

Show a summary per file

File	Description
internal/tracing/fanout.go	Consolidates concurrent exporter iteration + error joining into forEachExporter, simplifying ExportSpans and Shutdown.
internal/tracing/fanout_test.go	Adds targeted coverage for forEachExporter to ensure all exporters are invoked and errors are returned.

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• Files reviewed: 2/2 changed files
• Comments generated: 0