public function mailPlanning($id)
 {
     $waiters = Waiter::all();
     $planning = Planning::find($id);
     $waiters = $this->planningWaiters($waiters, $id, $planning);
     //mail to all waiters
     foreach ($waiters as $waiter) {
         Mail::send('emails.planning', ['user' => $waiter, 'waiters' => $waiters, 'planning' => $planning], function ($m) use($waiter) {
             $m->from(env('MAIL_FROM'), env('MAIL_NAME'));
             $m->to($waiter->email, $waiter->name)->subject('Your Reminder!');
         });
     }
     return redirect()->back();
 }