public function addUsers($id, Request $request)
 {
     $users = $request->input('users');
     $roster_data = Roster::where('id', '=', $id)->first();
     $roster = Roster::find($id)->users();
     foreach ($users as $user) {
         $roster->attach($user);
         Notification::add($user, 'CREATE_EVENT', ['start' => Common::formatDateTimeForSQL($roster_data->start_time), 'end' => Common::formatDateTimeForSQL($roster_data->end_time), 'admin_id' => Auth::user()->id]);
     }
     return response()->json(Roster::where('id', $id)->with('users')->first()->toArray()['users'], 200);
 }