/**
  * Responds to requests to GET /profile/favorite-exercises
  */
 public function getFavoriteExercises()
 {
     $current_user = Auth::user();
     $favorite_exercises = FavoriteExercise::with('exercise')->where('user_id', $current_user->id)->get();
     return view('profile.favorite-exercises', ['favorite_exercises' => $favorite_exercises]);
 }
 /**
  * Responds to requests to POST /exercises/favorites/{id}
  * Works like a toggle if exercise not in favorite->adds it,
  * otherwise removes from favorite
  */
 public function postFavorite($id)
 {
     $user = Auth::user();
     $favorite = FavoriteExercise::where('user_id', $user->id)->where('exercise_id', $id)->first();
     if ($favorite) {
         $favorite->delete();
         return response()->json(['result' => false]);
     } else {
         $favorite = new FavoriteExercise();
         $favorite->user_id = $user->id;
         $favorite->exercise_id = $id;
         $favorite->save();
         return response()->json(['result' => true]);
     }
 }