public function index()
{
$classroomIds = Auth::user()->joinedClassrooms;
$activities = Activity::whereIn('classroom_id', $classroomIds)->orderBy('created_at', 'DESC')->paginate(10);
$discussions = Discussion::where('parent_id', '')->whereIn('classroom_id', $classroomIds)->orderBy('created_at', 'DESC')->paginate(10);
return view('user.global.feeds', compact('activities', 'discussions'));
}