Support for custom http client

[paiyar]

Summary

Instead of always defaulting to http.DefaultClient, allowing passing one during NewClient configuration

Use cases

This would allow one to specify a custom roundtripper without mutating the http.DefaultClient global variable, this could be useful for adding certificates for custom endpoints that use self-signed certificates or are missing intermediaries.

Proposed solution

Simply allow passing an http client in the New* constructors

Is there a workaround to accomplish this today?

Mutate the global http.DefaultClient which is bad practice and has unintended side-effects for shared code

References & Prior Work

Nope