api for grouping centers, select centers as group in "pick centers" step

for exports

Export/ExportManager.php

@@ -563,7 +563,7 @@ class ExportManager
      */
     public function getPickedCenters(array $data)
     {
-        return $data[PickCenterType::CENTERS_IDENTIFIERS];
+        return $data;
     }
     
     /**