Set up DRF API for account app

[hexvolt]

Set up Django Rest Framework API for account application

[hexvolt]

Use cases:

• [x] list all user bank accounts (along with bank name): GET /banks/ (nested resource)
• [x] filter by bank or currency: GET /banks/1/accounts?currency=...
• [x] create bank account: POST /banks/1/accounts
• [x] update bank account: PUT /banks/1/accounts/2/
• [x] delete user's bank account: DELETE /banks/1/accounts/2/
• [x] search by name: GET /banks/1/accounts?search=...