Honor OTLP log document metadata

[felixbarny]

Summary

• Honor elasticsearch.document_id for OTLP logs by applying it to the index request id.
• Honor elasticsearch.ingest_pipeline for OTLP logs by applying it as the index request pipeline.
• Treat both attributes as document metadata so they are not serialized into OTLP log documents.

Test plan

• ./gradlew :x-pack:plugin:otel-data:test --tests "org.elasticsearch.xpack.oteldata.otlp.OTLPLogsTransportActionTests"
• ./gradlew :x-pack:plugin:otel-data:test --tests "org.elasticsearch.xpack.oteldata.otlp.OTLPLogsTransportActionTests" --tests "org.elasticsearch.xpack.oteldata.otlp.OTLPTracesTransportActionTests"
• ./gradlew :x-pack:plugin:otel-data:test --tests "org.elasticsearch.xpack.oteldata.otlp.OTLPLogsTransportActionTests" --tests "org.elasticsearch.xpack.oteldata.otlp.docbuilder.LogDocumentBuilderTests"
• ./gradlew :x-pack:plugin:otel-data:spotlessJavaCheck

[elasticsearchmachine]

Pinging @elastic/es-storage-engine (Team:StorageEngine)

[elasticsearchmachine]

Hi @felixbarny, I've created a changelog YAML for you.

[github-actions]

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[github-actions]

ℹ️ Important: Docs version tagging

👋 Thanks for updating the docs! Just a friendly reminder that our docs are now cumulative. This means all 9.x versions are documented on the same page and published off of the main branch, instead of creating separate pages for each minor version.

We use applies_to tags to mark version-specific features and changes.

Expand for a quick overview

When to use applies_to tags:

✅ At the page level to indicate which products/deployments the content applies to (mandatory)
✅ When features change state (e.g. preview, ga) in a specific version
✅ When availability differs across deployments and environments

What NOT to do:

❌ Don't remove or replace information that applies to an older version
❌ Don't add new information that applies to a specific version without an applies_to tag
❌ Don't forget that applies_to tags can be used at the page, section, and inline level

🤔 Need help?

• Check out the cumulative docs guidelines
• Reach out in the #docs Slack channel

[sidosera]

I'm not sure there’s much value in putting those functions in a standalone class, since they aren't useful outside the OTLPLogsTransportAction context. I actually prefer local extractDocumentId.

[felixbarny]

The span doc builder also supports the document_id, which is why I think the shared helper makes sense.