Marks an invoice as paid for logging purposes only, without generating any
accounting journals. Use it when the supplier was settled outside Rivage
(e.g. directly by the tenant).

The invoice status becomes paid and manually_marked_paid_at is set, which
keeps it out of the missing-accounting-entry consistency checks. No payment
order and no accounting entries are produced. For a settlement that must be
booked, use validate with the appropriate payment_method instead.