create a new account for existing customers in the bank

[AhmadElIdrissiAmiri]

As an existing bank customer. I want to create a new account so that i can deposit and withdraw money from that account
** Acceptance Criteria**
Scenario 1: successful account created
Given the user has a verified username and are of age greater than or equal to 18
When they request a new bank account
Then a new bank account is created with a unique 10-digit is and zero balance

Scenario 2: unsuccessful account creation due to customer being below 18:
Given the user has a verified username but is below 18
When they request a new bank account
Then no bank account is created and an error messages is displayed

Scenario3: unsuccessful account creation due to invalid username
Given the user does not have a verified username and is abive 18
When they request a new bank account
Then no bank account is created and an error message is displayed

Tasks

1. Create a class does a bank that can maintain accounts and usernames
2. create a method for creating a new bank account and adding it to the bank's existing accounts
3. create a test class to verify the customr