protected function addDefaultSpecifications(RequirementContract $requirement)
    {
        return $requirement->add(new Specifications\WritableStorage($this->app))
                ->add(new Specifications\WritableBootstrapCache($this->app))
                ->add(new Specifications\WritableAsset($this->app))
                ->add(new Specifications\DatabaseConnection($this->app))
                ->add(new Specifications\Authentication($this->app));
    }