code: public function addConfiguration(NodeDefinition $node)
      {
          parent::addConfiguration($node);
          $node
              ->children()
                  ->booleanNode('is_rotatable')
                      ->info('If true, the service will be a rotatable key, else just storable.')
                      ->defaultFalse()
                  ->end()
                  ->integerNode('nb_keys')
                      ->info('Number of keys in the key set.')
                      ->isRequired()
                      ->min(1)
                  ->end()
                  ->scalarNode('storage_path')->isRequired()->end()
                  ->arrayNode('key_configuration')
                      ->defaultValue([])
                      ->useAttributeAsKey('key')
                      ->prototype('variable')->end()
                  ->end()
              ->end();
      }
docs: {@inheritdoc}