public function downgrade(Request $request, $course_id)
 {
     $course = Course::find($course_id);
     $user = User::find($request->user_id);
     $user_id = $request->user_id;
     $user->courses()->updateExistingPivot($course_id, ['level' => 0]);
     $test = CourseUser::where('user_id', $user_id)->where('level', 1)->count();
     if ($test == 0 && $user->level->level == 2) {
         if (!empty(Band::where('user_id', $user_id)->first())) {
             $user->level_id = 2;
         } else {
             $user->level_id = 1;
         }
         makeModification('users', printUserLinkV2($user) . ' is no longer a teacher.');
         $user->save();
     }
     CourseModification::create(['author_id' => Auth::user()->id, 'user_id' => $user_id, 'course_id' => $id, 'value' => 5]);
     Flash::success("{$user->first_name} {$user->last_name} est maintenant un élève du cours ucfirst({$course->name})");
     return redirect('admin/courses/' . $course->slug . '/members');
 }