BookStackApp/BookStack

class AppServiceProvider extends ServiceProvider
{
    public function boot()
    {
        //
        Relation::morphMap([
            'BookStack\\Bookshelf' => Bookshelf::class,
            'BookStack\\Book'      => Book::class,
            'BookStack\\Chapter'   => Chapter::class,
            'BookStack\\Page'      => Page::class,
        ]);
        //
    }
    //
}