This module contains all of the domain objects required to build our application; it's a good idea to keep them separated, as another module. By doing this, you can later include the module as a dependency of other modules, which will help to avoid writing the same code twice. The following diagram shows the contents of this module:

As you can see, this module contains only two classes. The Credentials class is used as the payload, to authenticate a user and retrieve the JSON web token, and the BalanceInformation class contains the payload resultant of querying the customer account balance.