Can now download from all banks registered on the banks/nordigen table
and write to the PostgresSQL DB (or any DB, since we're now agnostic).
Commented out most of the managers functions until the integration with
the new DB client is complete.
Set Optional relationships. Remove the DB types as dataclasses, it only
increased the verbosity of the types w/o much going for it.
Change the name Original to Transaction, since the type is the
placeholder for the rest of the transaction information.
