protected function bootstrapSidebarPlaceholders(Application $app)
    {
        $widget = $app->make('orchestra.widget');
        $placeholder = $widget->make('placeholder.orchestra.extensions');

        $this->attachListenerOn($app, 'form', function () use ($placeholder) {
            foreach ($this->sidebar as $name => $view) {
                $placeholder->add($name)->value(\view($view));
            }
        });
    }