def build_credit_note(credit_note = {})
      case credit_note
        when CreditNote then     credit_note.gateway = self
        when Hash then        credit_note = CreditNote.new(credit_note.merge(:gateway => self))
      end
      credit_note
    end
def build_credit_note(credit_note = {})
      case credit_note
        when CreditNote then     credit_note.gateway = self
        when Hash then        credit_note = CreditNote.new(credit_note.merge(:gateway => self))
      end
      credit_note
    end
Factory method for building new CreditNote objects associated with this gateway.