Add users table
Add User model
Add Song model
Add songs table
Add Artist model
Add artists table
Add artist_id to songs table
Add uniqueness constraint to songs table
Add uniqueness validation to Song model
Add associations between Artist and Song models
Add FavoriteSong model
Add favorite_songs table
Add associations with FavoriteSong
Add Genre model
Extract genre names into constant
Add genres table
Add genre_id to songs
Add associations w/ Genre