Fix/clippy

[yubiuser]

Fixes the clippy warning that occur with v1.78. being the new stable. This made the test fail (e.g here). Addressed the following warnings:

• https://rust-lang.github.io/rust-clippy/master/index.html#/to_string_trait_impl
• https://rust-lang.github.io/rust-clippy/master/index.html#/assigning_clones
• https://rust-lang.github.io/rust-clippy/master/index.html#/incompatible_msrv
• https://rust-lang.github.io/rust-clippy/master/index.html#/derivable_impls

Sidenote: set the environment variables RUST_BACKTRACE and RUSTFLAGS in the devcontainer the same as they are in the github action workflow file.

[roderickvd]

Perfect, thanks!