Make DefaultHttpClient extensible, Issue #754

[noetro]

Changes

The package scoped constructor of DefaultHttpClient has been made protected so that custom implementations can extend DefaultHttpClient to provide a pre-build OkHttp client delegate.

I considered making the constructor public so we didn't need to extend, but that felt like a step too far and leaks to the world that the DefaultHttpClient implementation is using OkHttp

References

Please include relevant links supporting this change such as a:

https://github.com/auth0/auth0-java/issues/754

Testing

The existing automated tests run.

• [ ] This change adds test coverage
• [X] This change has been tested on the latest version of the platform/language

Checklist

• [X] I have read the Auth0 general contribution guidelines
• [X] I have read the Auth0 Code of Conduct
• [X] All existing and new tests complete without errors

[tanya732]

Hi @noetro

Thank you for raising the PR, I'll review it shortly.