adjustment.rb

    def update!(target = nil)
      return amount if closed?
      if source.present?
        amount = source.compute_amount(target || adjustable)
        self.update_columns(
          amount: amount,
          updated_at: Time.now,
        )
        if promotion?
          self.update_column(:eligible, source.promotion.eligible?(adjustable))
        end
      end
      amount
    end