Jackett: [enhancement] BitTorrent v2 support

[ilike2burnthing]

https://blog.libtorrent.org/2020/09/bittorrent-v2/

Definitely no rush on this, as hybrid torrents and magnets will probably be favoured over v2-only, and even that will take time, but we should be aware that v2 will see magnet links change from:

magnet:?xt=urn:btih:

to:

magnet:?xt=urn:btmh:

I don't think anything else here really affects Jackett, and it's probably going to be more of a case of adding support per indexer when their site adds it, rather than anything global on our part (feel free to correct me if I'm wrong there). At the least though, this serves as heads up.

[ngosang]

I can do the changes in the code when the first torrent site implements it.
We have to think:

• If one site provides v1 and v2 magnets we should favor v1? v2? or add a new field to include both?
• Add new icon in the UI to distinguish between v1 and v2?

[ilike2burnthing]

I would imagine that any site wanting to support both will just use the hybrid version rather than 2 separate ones, but as you say we'll have to wait and see.

At this early stage we should probably aim for the greatest compatibility without confusing the average user, so if a site does provide a combination, this would be my suggestion:

• v1 & v2 - default to v1 with an indexer option to use v2 instead
• v1 & hybrid - default to hybrid with an indexer option to use v1 instead
• v2 & hybrid - default to hybrid with an indexer option to use v2 instead
• all 3 - default to hybrid with an indexer radio option to choose v1, v2, or hybrid