Enable paying for auction invoices via bank transfer

[vohmar]

To enable participating in auctions for users that do not have access to a payment card nor any of the open banking options we have available we should enable paying the invoices using bank transfer. Deposit payments are excluded from the scope of this issue

1. Adding bank transfer option to the portal: separate button to the invoice view - perhaps as a grey button before 'send e-invoice'. Button press should open new view/overlay/popup with payment details: recipient name, iban, bic/swift, bank address, payment description (identifier as the first value, the rest is up to the payer), payment sum
2. Identifying the source of the payment: we require putting a payment identifier (invoice nr) as the first value on the payment description field
3. Getting the info about received payment: LHV-connect
4. What to do if the paid sum does not match the invoice due sum: return the sum to the payer via lhv-connect

First iteration of this covers paying each invoice separately, later we should add bulk payment as well