Returned data more clearer + getUserPlaylists

[SharkyFlou]

Describe your changes

The return data of getPlaylistTracks used for now by getTopTrends is now more clearer and so easier to use by the front-end.

New functionnality : getUserPlaylists

Checklist before requesting a review

• [x] I have performed a self-review of my code
• [x] I have read the PULL_REQUEST_TEMPLATE as well as the CODE_OF_CONDUCT
• [ ] If it is a core feature, I have added thorough tests.