Re: [PATCH 2/6] ci: check formatting of our Rust code

> Introduce a CI check that verifies that our Rust code is well-formatted.
> This check uses rustfmt(1), which is the de-facto standard in the Rust
> world.
>
> The rustfmt(1) tool allows to tweak the final format in theory. In
> practice though, the Rust ecosystem has aligned on style "editions".
> These editions only exist to ensure that any potential changes to the
> style don't cause reformats to existing code bases. Other than that,
> most Rust projects out there accept this default style of a specific
> edition.
>
> Let's do the same and use that default style. It may not be anyone's
> favorite, but it is consistent and by making it part of our CI we also
> enforce it right from the start.
>
> Note that we don't have to pick a specific style edition here, as the
> edition is automatically derived from the edition we have specified in
> our "Cargo.toml" file.