Feature: checking and investment account interaction

[leograba]

The concept of checking account and investment account must be added to the project. This ticket takes care of describing the logic for checking and investment account interaction.

Checking account: It is the sum of all cash and money held in bank accounts.
Investment account: It is the sum of all money invested somehow.

The features below have to be added to the application logic and DB:

• have only one of each accounts per login. Multiple checking or investment accounts are not allowed.
• Whenever money is invested, it is automatically transferred to the investment account.
  • Add an entry to the investment acccount. Automatic category is "unnalocated".
• Whenever money is redeemed from an investment two outcomes are possible:
  • Reallocation to another investment, in which case only the investment category is changed.
  • Withdrawal to a checking account, in which case an entry is automatically added to the checking account. Automatica category is "investment"