[Java] Can't generate a ApiClient with specifying a default ReadTimeout

Description

I use maven builder with swagger-codegen to generate service client. But in my case, I want to specify some api with a default ReadTimeout within 3 secs. I don't want to code when new a ApiClient and set the readTimeout because it's a general config in many components. So base on SRP, I need to set a default value in ApiClient

Version

3.0.0-rc1

Suggest a fix/enhancement

    public ApiClient() {
        httpClient = new OkHttpClient();
        httpClient.setReadTimeout($readTimeout)
    ...
   }

Start by locating the Java ApiClient template used by swagger-codegen and the generated client's OkHttp setup. Check how generated client configuration is represented, then define what should be considered done for supplying a default read timeout and verify the generated client behavior with the relevant Maven tests, if available.