Allow only one bank account per user account
This changes BankAccount from ForeignKey to OneToOneField so that each user account can have only one bank account, not many. We still don't have use cases to allow multiple bank accounts per user.
To review this
- run tests (though right now I get 8 failures for
January
/December
, and 1 for a missingInvoiceTemplate
object, both unrelated) - check the code
- test in admin: add, delete
- run
generate_account_data
- maybe check API (though now it's failing with
'InvoiceViewSet' should either include a
serializer_classattribute
)