Added opus to supported mimetymes and extensions

See merge request funkwhale/funkwhale!806

Resolve "Importing tracks without album fails"

See merge request funkwhale/funkwhale!803

Cherry pick develop

See merge request funkwhale/funkwhale!802

Resolve "Clicking on playlist name from PlaylistModal does nothing if current page is that playlist's page"

Fix #833: broken translation on homepage

See merge request funkwhale/funkwhale!784

Resolve ""This backend doesn't support absolute paths" when uploading certain tracks"

See merge request !785

Fix #814: Added copy-to-clipboard button with Subsonic password input

See merge request funkwhale/funkwhale!783

Fix #855: secondary menus truncated on narrow screens

See merge request funkwhale/funkwhale!782

Fix #847: Use ASCII filename before upload to S3 to avoid playback issues

See merge request funkwhale/funkwhale!778

Fix #835: Hide pod statistics on about page if those are disabled

See merge request funkwhale/funkwhale!780

Fix #851: wrong og:image url when using S3 storage

See merge request funkwhale/funkwhale!777

Fix #848: Fixed invalid file extension for transcoded tracks

See merge request funkwhale/funkwhale!776

Fix #850: Ensure empty but optional fields in file metadata don't error during import

See merge request funkwhale/funkwhale!775

Develop cherry pick

See merge request funkwhale/funkwhale!774