[BUG] indices.existsAlias types are not correct

[pveller]

What is the bug?

The types for indices.existsAlias are not correct.

This is a HEAD method and result.body will be set to a boolean based on the response status:

https://github.com/opensearch-project/opensearch-js/blob/main/lib/Transport.js#L396

The types suggest otherwise:

https://github.com/opensearch-project/opensearch-js/blob/main/api/indices/existsAlias.d.ts#L34

[nhtruong]

Thanks for bring this up. All API functions and their types are generated from the API Spec which causes a mismatch for this kind of functions because they are handled differently (i.e. returning a boolean instead of the response from server). We'll update the code-generator to account for this.