Enable the setting of an OkHttpClient on API-Level to allow more customization

[BenchmarkingBuffalo]

Hey there,
when using this SDK, I am running into the situation of not being able to customize the OkHttpClient which is used in the several ApiClient-Classes.
I am used to the behavior of the openapi-generator where you can set the HttpClient on API-Level using a simple Setter.
This would allow to customize the HttpClient used in the API.
Can you please add this functionality?

[dasheck0]

Thanks for opening this issue. We will look into this and provide you some feedback. Allowing some customization to the http client seems like a good thing to do, so very positive on this.