public function registerObserverServiceProvider()
    {
        if (! $this->files->exists(app_path('Providers/ObserverServiceProvider.php'))) {
            $this->call('make:provider', [
                'name' => 'ObserverServiceProvider',
            ]);
            $this->info('Please register your ObserverServiceProvider in config/app.php.');
            $this->info('Do run php artisan config:cache to make sure ObserverServiceProvider is loaded.');
        } else {
            $this->info(app_path('Providers/ObserverServiceProvider.php') . ' already exist.');
        }
    }