Protected Credit Card logging

We've added logging in two operations on `ProtectedCreditCard` object: `#save` and `#just_click_shop`. It is gonna save the given request data and the response from the SOAP calls.

Once we put our hands on the logged operations from the production env, we will be able to reproduce the official XML response on the fake-braspag webservice.
According to the WSDL, the response will present only one value, the saved card's just click key.