public function addConfigurationSection(ArrayNodeDefinition $node)
    {
        $node
            ->addDefaultsIfNotSet()
            ->children()
                ->scalarNode('website_name')->cannotBeEmpty()->defaultValue('Qcm Demo')->end()
                ->arrayNode('configuration')
                    ->addDefaultsIfNotSet()
                    ->children()
                        ->scalarNode('max_questions')->cannotBeEmpty()->defaultValue(40)->end()
                        ->arrayNode('question_level')
                            ->useAttributeAsKey('level')
                            ->prototype('scalar')->end()
                        ->end()
                        ->scalarNode('answers_max')->cannotBeEmpty()->defaultValue(5)->end()
                        ->scalarNode('timeout')->cannotBeEmpty()->defaultValue(2400)->end()
                        ->scalarNode('time_per_question')->cannotBeEmpty()->defaultValue(60)->end()
                    ->end()
                ->end()
            ->end();
    }