User data export + followers I/O

[rhaamo]

An user should be able to get an archive of:

• All original track files
• Tracks artworks
• User avatar
• user.json with profile
• tracks.json with tracks infos

Possible issue : the archive will be more-or-less the same size of all the user tracks, disk space should be checked before generating it through celery.

We will introduce the celery beat to periodically remove the archive after 5 days of the generation.

Creating an archive should check ((disk space avail)-(max space used by queued archives to generate)) > (space of archive to generate).

An user should be able to export their following list. (in text file, like mastodon) And it should be able to import that same list. (in text file, like mastodon)