proxyAuthenticator field is not exposed by DefaultOpenAiClient

[Andreas54321]

Is your feature request related to a problem? Please describe.
To use the library i need to authenticate to an proxy. The used okHttp client provides a authenticator field for this.

Describe the solution you'd like
Please forward the field proxyAuthenticator.

Describe alternatives you've considered
Extending DefaultOpenAiClient and instaniating the http client did not work because of too much internal dependencies.

Additional context
none