Allow (expose) customizing the `OkHttpClient.Builder` required e.g. for `addInterceptor()` to support Observability (e.g. with Micrometer)

[vorburger]

The library currently does not "expose" the OkHttpClient.Builder from com.google.genai.ApiClient.

This makes it impossible to use (e.g.) Micrometer for Observability - or do any other "transport customization".

(It may be possible with private reflection hacking, but that's really super ugly, of course, and should be avoided.)

@jaycee-li would we consider a contribution to allow this? (With a TBD design, of course.)

PS: #635 suggested this in the past already (/CC @kawolum).

[hemasekhar-p]

Hi @vorburger, Thank you for bringing this, we'll be filing a feature request internally to track it. it's currently under review. We'll keep you informed of any updates.