/**
  * {@inheritDoc}
  */
 public function addConfiguration(ArrayNodeDefinition $builder)
 {
     parent::addConfiguration($builder);
     $builder->beforeNormalization()->ifString()->then(function ($v) {
         return array('driver' => $v);
     })->end()->children()->scalarNode('driver')->isRequired()->cannotBeEmpty()->end()->end();
 }
 /**
  * {@inheritdoc}
  */
 public function addConfiguration(ArrayNodeDefinition $builder)
 {
     parent::addConfiguration($builder);
     $builder->children()->scalarNode('storage_dir')->isRequired()->cannotBeEmpty()->end()->scalarNode('id_property')->defaultValue(null)->end()->end();
 }