[Search] Playground sends telemetry headers with completion requests

[sphilipse]

Summary

Playground now sends the X-Elastic-Product-Use-Case header with a search_playground for telemetry purposes.

Checklist

Check the PR satisfies following conditions.

Reviewers should verify this PR satisfies this list as well.

• Any text added follows EUI's writing guidelines, uses sentence case text and includes i18n support
• Documentation was added for features that require explanation or tutorials
• Unit or functional tests were updated or added to match the most common scenarios
• If a plugin configuration key changed, check if it needs to be allowlisted in the cloud and added to the docker list
• This was checked for breaking HTTP API changes, and any breaking changes have been approved by the breaking-change committee. The release_note:breaking label should be applied in these situations.
• Flaky Test Runner was used on any tests changed
• The PR description includes the appropriate Release Notes section, and the correct release_note:* label is applied per the guidelines

Identify risks

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Describe the risk, its severity, and mitigation for each identified risk. Invite stakeholders and evaluate how to proceed before merging.

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• ...

[elasticmachine]

💚 Build Succeeded

• Buildkite Build
• Commit: 709d8ad

Metrics [docs]

Public APIs missing comments

Total count of every public API that lacks a comment. Target amount is 0. Run node scripts/build_api_docs --plugin [yourplugin] --stats comments for more detailed information.

id	before	after	diff
@kbn/inference-langchain	48	49	+1

Unknown metric groups

API count

id	before	after	diff
@kbn/inference-langchain	49	50	+1

History

• 💛 Build #302060 was flaky 82f76f9
• 💔 Build #301963 failed b26cca9
• 💔 Build #301838 failed 1df2ed8

[darnautov]

LGTM