Add responses for client tests

[Gonmeso]

Currently anything related to an outbound requests is fully mocked so encoding errors can arise as the tests don't even attempt the request.

Using responses we can mock the response for and endpoint, but requests internals are still in place so if any error comes from our side when performing the request they should arise in the tests.

[stevencartavia]

Hi, is this issue still unresolved?

[Gonmeso]

Hi @stevencartavia it is still unresolved so feel free to pick it up!