re: having `Suretax::Api::Response` and `Suretax::Response`, I think one of them should go away... the question is which one.  My first inclination is to merge the latter into the former as, in reality, you can't have a Response outside of talking to the Api.  The only problem then is you'll have a massive `Suretax::Api::Response` class which is no good.  You can start there, and see if you can separate the concerns of the resulting class. Maybe that means more http level concerns vs. what's going on in the body i.e. moving parsed json into different objects like TaxAmount, stripping xml, etc.