Fix N+1 issue on API of current playlist songs

app/controllers/api/v1/current_playlist/songs_controller.rb

@@ -4,7 +4,12 @@ module Api
   module V1
     class CurrentPlaylist::SongsController < ApiController
       def show
+        favorite_playlist = Current.user.favorite_playlist
+
         @songs = Current.user.current_playlist.songs
+          .includes(:artist, :album)
+          .joins("Left JOIN playlists_songs T1 ON songs.id = T1.song_id AND T1.playlist_id = #{favorite_playlist.id}")
+          .select("songs.*, T1.playlist_id IS NOT NULL as is_favorited")
       end
     end
   end

app/views/api/v1/current_playlist/songs/show.json.jbuilder

@@ -1 +1 @@
-json.array! @songs, partial: "api/v1/songs/song", as: :song
+json.array! @songs, partial: "api/v1/songs/song", as: :song, cache: true

app/views/api/v1/songs/_song.json.jbuilder

@@ -1,8 +1,8 @@
 json.call(song, :id, :name, :duration)
-json.url new_api_v1_stream_path(song_id: song.id)
+json.url new_api_v1_stream_url(song_id: song.id)
 json.album_name song.album.title
 json.artist_name song.artist.title
-json.is_favorited Current.user.favorited? song
+json.is_favorited song.respond_to?(:is_favorited) ? song.is_favorited : Current.user.favorited?(song)
 json.format need_transcode?(song.format) ? Stream::TRANSCODE_FORMAT : song.format
 json.album_image_url do
   json.small URI.join(root_url, image_url_for(song.album, size: "small"))