Extension 6: Savings account

In this extension savings accounts are introduced into the banking system. Existing customers should be able to open savings accounts that are connected to their regular accounts. The way that ING works however is that this does not create a separate bank account for the savings account, but it rather adds a savings account under the checkings account with the same IBAN.

In this extension I had to implement the savings accounts, implement paying interest over the balance on the savings accounts and refactoring a whole system to use the new account system.