rust-clippy: refactor complex type This makes reading the signature a bit less tiring.

rust-clippy: simplify return type of debug function This makes the type a little bit more readable.

rust-clippy: add `is_empty` method to please the `clippy` gods I can see it being useful anyway.

rust: don't use a reference to a `Cow` This was caught by `clippy`.

rust-clippy: reassure `clippy` that 8 arguments is expected This API is a bit verbose, but refactoring it into a struct isn't better in this particular case IMO, and there is a lot of info to pass.

rust-clippy: use `write_all` since we're not expecting a partial write Clippy caught this. This is a good lint in general, but here this was not really a bug in this example code.