feat: FW-57 retrieve existing playlists

[barroro]

• Create PlaylistsHTTPClient with searchPlaylists method to retrieve all the existing playlists.
• Create a new API route to retrieve existing playlists using PlaylistsHTTPClient.
• Create the Playlist entity.

[DanielMoraDC]

LGTM, good job 🚀

There is a bit of duplication but I would say that we abstract the clients whenever we see a third use case that can benefit from that, so we avoid adding too much complexity early on.