static function add($newsletterTypeID, $subscriptionListID, $status = eZNewsletterType::StatusDraft)
 {
     $existing = eZNewsletterTypeSubscription::fetch($newsletterTypeID, $subscriptionListID, $status);
     if (!$existing) {
         $newAssignment = new eZNewsletterTypeSubscription(array('newsletter_id' => $newsletterTypeID, 'subscription_id' => $subscriptionListID, 'status' => $status));
         $newAssignment->store();
     }
 }