rewrite export controller and manager

- upgrade to symfony 4 ;
- add support for directExportInterface

Export/ExportManager.php

@@ -148,12 +148,18 @@ class ExportManager
      * 
      * @internal used by DI
      * 
-     * @param ExportInterface $export
+     * @param ExportInterface|DirectExportInterface $export
      * @param type $alias
      */
-    public function addExport(ExportInterface $export, $alias)
+    public function addExport($export, $alias)
     {
-        $this->exports[$alias] = $export;
+        if ($export instanceof ExportInterface || $export instanceof DirectExportInterface) {
+            $this->exports[$alias] = $export;
+        } else {
+            throw new \InvalidArgumentException(sprintf("The export with alias %s "
+                . "does not implements %s or %s.", $alias, ExportInterface::class, 
+                DirectExportInterface::class));
+        }
     }
     
     /**
@@ -426,6 +432,11 @@ class ExportManager
         //$qb = $this->em->createQueryBuilder();
         $centers = $this->getPickedCenters($pickedCentersData);
         
+        if ($export instanceof DirectExportInterface) {
+            return $export->generate($this->buildCenterReachableScopes($centers, $export),
+                $data[ExportType::EXPORT_KEY]);
+        }
+        
         $query = $export->initiateQuery(
                 $this->retrieveUsedModifiers($data), 
                 $this->buildCenterReachableScopes($centers, $export),