[Pkg-rust-maintainers] Bug#1094490: rust-idna - updating to version 1 and choice of backend.

[Peter Green]

Package: rust-idna
Severity: important

It seems like it would be a good idea to upgrade the idna crate to version 1,
version 0.5 has a "security" issue and the new version of rust-url, which has
been requested by jonas needs version 1.

rust-idna 1 supports multiple backends with the backend being chosen by the
version of the idna-adapter crate. There are three options.

1.0 - no unicode backend, afaict this would be a downgrade compared to the current situation)
1.1 - unicode-rs backend, this would be essentially what we have now.
1.2 - icu backend, this is the upstream default

Whichever backend we select we will have at least two NEW crates.
idna_adapter and utf8_iter

If we choose the unicode-rs backend we will additionally need the
NEW idna_mapping crate.

If we choose the icu backend we will additionally need a bunch of
NEW icu crates.