code: private function getDueClauses()
      {
          $ex = new Expr();
  
          return $ex->orX(
              $ex->andX(
                  $ex->eq('t.trigger', ':trigger_invoiced'),
                  $ex->in('o.invoiceState', ':state_invoiced')
              ),
              $ex->andX(
                  $ex->eq('t.trigger', ':trigger_fully_invoiced'),
                  $ex->eq('o.invoiceState', ':state_fully_invoiced')
              ),
              $ex->andX(
                  $ex->eq('t.trigger', ':trigger_shipped'),
                  $ex->in('o.shipmentState', ':state_shipped')
              ),
              $ex->andX(
                  $ex->eq('t.trigger', ':trigger_fully_shipped'),
                  $ex->eq('o.shipmentState', ':state_fully_shipped')
              )
          );
      }
docs: Returns the due clause:
  - payment term triggered
  - payment date lower than or equal today
  
  @return Expr\Base