add mime types to documents

Form/StoredObjectType.php

@@ -22,6 +22,7 @@ class StoredObjectType extends AbstractType
     {
         $builder
             ->add('filename', AsyncUploaderType::class)
+            ->add('type', HiddenType::class)
             ->add('keyInfos', HiddenType::class)
             ->add('iv', HiddenType::class)
             ;