What Goes in Active Records Part 2

In the second part of this series, we'll actually remove the various parts of the model that don't belong, as shown in the part 1. Most of the time will be spent removing the two ActiveRecord callbacks, replacing them with a class that sits between the controller and model, mediating the lifecycle of the User and Braintree API objects. We'll also briefly replace the other two methods with implementations outside the ActiveRecord class.