Bank accounts should be visible in the involved parties field

[kefcom]

When booking bank transfers we need to specify between which bank accounts the money is transferred. I suggest adding the bank accounts as a source field in the 'members' dropdown.

[BerendWouters]

The internal bank account transfer is a difficult one. We designed it as two separate transactions, since a transaction is always between 1 bank account and one (un)known party (typically members).
The frontend could be improved by creating a separate option next to the "Debet" and "Credit" action called "Bank transfer", allowing to interact between two bank accounts, but in the database (and thus in the transaction overview) as two separate transactions.