fix: tracker URLs in magnet are url-encoded

[angrynode]

I think this solves the problem in #553

If you think this PR is ok, i can add docs before merging.

[casey]

Thanks for the PR! Docs would be great.

One thing that's odd to me is the form_urlencoded crate. As far as I know, form encoding and URL encoding are at least slightly different and not interchangeable. Unless that's not the case, I would suggest using the urlencoding crate.

Don't worry about the clippy failures on CI, I'll get those in another PR.

[casey]

Lints fixed in #555, updated the branch.

[angrynode]

I rebased on the latest commit instead of adding a merge commit (personal preference to keep a reduced git log, let me know if that's inappropriate).

I added some doc comments explaining the url-encoding. Let me know if i should add more docs somewhere.

I think form_urlencoded is the correct choice. I believe the magnet URI query is inspired by the HTTP URL queries which adhere to this standard. That's already what you're using in MagnetLink::parse when iterating over Url::query_pairs which uses that crate to decode the key/values. There may be subtleties i'm not aware of.

[casey]

I rebased on the latest commit instead of adding a merge commit (personal preference to keep a reduced git log, let me know if that's inappropriate).

Totally fine, I always squash before merging.

I removed the comments, I pretty much reserve comments for things which are super confusing.