Add codegen_name to unified_inference API

[pquentin]

@flobernd did this for all endpoints in #2457, so I assume this is also needed for #3313, even though clients won't generate it for now. (Confusingly, this does not update schema.json, which makes me wonder how the .NET client uses this information.)

[github-actions]

Following you can find the validation results for the API you have changed.

API	Status	Request	Response
inference.unified_inference	⚪	Missing test	Missing test

You can validate this API yourself by using the make validate target.

[flobernd]

Thanks for taking care about this @pquentin!

For ValueBody like this, it should definitely emit the hint to the schema.json. The corresponding field is still in the metamodel as well:
https://github.com/elastic/elasticsearch-specification/blob/main/compiler/src/model/metamodel.ts#L316

Sounds like a bug to me.

[flobernd]

My generator shows a bunch of warnings as well:

WARN: Value body without codegen name in type '_global.get_source.Response'.
WARN: Value body without codegen name in type '_global.search_mvt.Response'.
WARN: Value body without codegen name in type 'esql.query.Response'.
WARN: Value body without codegen name in type 'ilm.get_lifecycle.Response'.
WARN: Value body without codegen name in type 'indices.disk_usage.Response'.
WARN: Value body without codegen name in type 'indices.downsample.Response'.
WARN: Value body without codegen name in type 'indices.get.Response'.
WARN: Value body without codegen name in type 'indices.get_alias.Response'.
WARN: Value body without codegen name in type 'indices.get_field_mapping.Response'.
WARN: Value body without codegen name in type 'indices.get_mapping.Response'.
WARN: Value body without codegen name in type 'indices.get_settings.Response'.
WARN: Value body without codegen name in type 'indices.get_template.Response'.
WARN: Value body without codegen name in type 'indices.promote_data_stream.Response'.
WARN: Value body without codegen name in type 'indices.recovery.Response'.
WARN: Value body without codegen name in type 'indices.resolve_cluster.Response'.
WARN: Value body without codegen name in type 'ingest.get_pipeline.Response'.
WARN: Value body without codegen name in type 'rollup.get_rollup_caps.Response'.
WARN: Value body without codegen name in type 'rollup.get_rollup_index_caps.Response'.
WARN: Value body without codegen name in type 'search_application.get_behavioral_analytics.Response'.
WARN: Value body without codegen name in type 'searchable_snapshots.clear_cache.Response'.
WARN: Value body without codegen name in type 'security.delete_privileges.Response'.
WARN: Value body without codegen name in type 'security.get_privileges.Response'.
WARN: Value body without codegen name in type 'security.get_role.Response'.
WARN: Value body without codegen name in type 'security.get_role_mapping.Response'.
WARN: Value body without codegen name in type 'security.get_service_accounts.Response'.
WARN: Value body without codegen name in type 'security.get_user.Response'.
WARN: Value body without codegen name in type 'security.put_privileges.Response'.
WARN: Value body without codegen name in type 'slm.get_lifecycle.Response'.

Looks like a regression. I'll debug the compiler next week and push a fix.