public function modifyWebRouter(Container $di)
{
    ...
    $router = $di->get('web_router');
    $router->add('structure', '/structure/fetch')
        ->setValues(['action' => 'fetch']);

    $router->add('structure.import', '/structure/import')
        ->setValues(['action' => 'import']);

    $router->add('structure.delete', '/structure/delete')
        ->setValues(['action' => 'delete']);
}