Allow invoices to have different addresses

This model will be used to store banking contact for invoices. It will allow us to create different invoices which should be paid for different people. We need this at the end of the 2023 season as the finances of the SUL get handed to a new person / account.

This commit also contains a migration which creates a new PayeeAddress with the address that was hardcoded in our template and attaches it to existing invoices, so that existing invoices don't change from a TO point of view.