[OAS] extract schemas as referenced components

[TinaHeiligers]

Summary

fix #244662

Implements OpenAPI Schema (OAS) componentization to extract inline schemas into reusable components with $ref references in merge_ess_oas.js and merge_serverless_oas.js.

The aim is to provide OAS docs that support tooling better for consuming teams generating clients from the OAS docs.

Change highlights

• Existing component traversal - Processes pre-existing components (e.g., bedrock_config, jira_secrets) to extract nested schemas

• HTTP method filtering - Explicit allowlist (get, post, put, patch, delete, head, options, trace)

• Object/composition handling - Extracts both object types and composition types (oneOf/anyOf/allOf)

• Structural field detection - Extracts all objects with meaningful structure, not just those with properties

• Component naming - Name generation includes with parentComponentName context to prevent collisions in nested schemas.

• Documentation - mostly in jsdocs

• enables unit testing! - oas_docs now supports jest tests 🎉

• Documentation was added for features that require explanation or tutorials (jsdocs)

• Unit or functional tests were updated or added to match the most common scenarios

Risks

• This PR changes the OAS yaml files, carrying a risk that the new format isn't fully supported.

Potential future work

• Introduce a --dry-run mode for preview and an --overwrite flag to either persist the changes explicitly.
• Add CI check to ensure MAX_RECURSION_DEPTH is not exceeded.
• Support previewing domain-specific OAS docs with inline schemas extracted to components

[jloleysens]

Hey @TinaHeiligers nice work, I did first pass of review and left a few comments. Mainly wanted to call out:

• Can we ensure we are also traversing into the existing schemas.components object
• Can we restructure our test strategy to rather make assertions like expect(schema).toEqual({ ... }). This would be a lot easier to follow and ensure that the tests are doing
• Can we revert the deletions of api_docs?

[jloleysens]

Thanks for addressing my feedback @TinaHeiligers ! Left a couple further comments

[jloleysens]

/ci

[elasticmachine]

Pinging @elastic/fleet (Team:Fleet)

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[TinaHeiligers]

needed to resolve external references because `redocly doesn't seem to handle it

[flash1293]

The streams change is kinda unrelated to the PR. Also, we shouldn't do this here, since this is about the streamlang syntax which isn't i18n-ified. Please either roll back or use {'includes'} / {'excludes'} to get rid of the warning

[TinaHeiligers]

@flash1293 I have no idea how that change got there! I'll be cleaning it up when the work resumes soon.

[TinaHeiligers]

closing as superseded by #258986