public static Song GetOrCreateSong(Song song, MusicStoreDb musicStoreDbContext)
        {
            Song existingSong = null;

            song.Artist = GetOrCreateArtist(song.Artist, musicStoreDbContext);

            if (song.Id != 0)
            {
                existingSong = musicStoreDbContext.Songs.FirstOrDefault(s => s.Id == song.Id);
            }
            else if (song.Title != null)
            {
                existingSong = musicStoreDbContext.Songs.FirstOrDefault(s => s.Title == song.Title);
            }

            if (existingSong != null)
            {
                return existingSong;
            }

            musicStoreDbContext.Songs.Add(song);
            musicStoreDbContext.SaveChanges();

            return song;
        }
        public static Artist GetOrCreateArtist(Artist artist, MusicStoreDb musicStoreDbContext)
        {
            Artist existingArtist = null;
            if (artist.Id != 0)
            {
                existingArtist = musicStoreDbContext.Artists.FirstOrDefault(a => a.Id == artist.Id);
            }
            else if (artist.Name != null)
            {
                existingArtist = musicStoreDbContext.Artists.FirstOrDefault(a => a.Name == artist.Name);
            }

            if (existingArtist != null)
            {
                return existingArtist;
            }

            musicStoreDbContext.Artists.Add(artist);
            musicStoreDbContext.SaveChanges();

            return artist;
        }
        public static Album GetOrCreateAlbum(Album album, MusicStoreDb musicStoreDbContext)
        {
            Album existingAlbum = null;

            if (album.Id != 0)
            {
                existingAlbum = musicStoreDbContext.Albums.FirstOrDefault(a => a.Id == album.Id);
            }
            else if (album.Title != null)
            {
                existingAlbum = musicStoreDbContext.Albums.FirstOrDefault(a => a.Title == album.Title);
            }

            if (existingAlbum != null)
            {
                return existingAlbum;
            }

            musicStoreDbContext.Albums.Add(album);
            musicStoreDbContext.SaveChanges();

            return album;
        }