converting `Dname` to lowercase

[Nicki Křížek]

I have an instance of possibly mixed-case Dname and I would like to get the lowercase version of it. Ideally, I would call some method like Dname::into_lowercase() to obtain it.

I have not found an easy way to do that with the existing API, but I might be missing something. So far, I just do the conversion like this:

let dname = Dname::bytes_from_str("eXaMPLe.Com").unwrap();
let dname_lowercase: Dname<Vec<u8>> = Dname::from_octets(
    dname
        .as_octets()
        .iter()
        .map(u8::to_ascii_lowercase)
        .collect(),
).unwrap();

It works, but it's a little cumbersome. Obtaining a lowercase version of a Dname seems like a common enough use-case to warrant some library function.

[Martin Hoffmann]

That seems like an oversight indeed. We will add two methods make_canonical which converts in place and to_canonical which returns a new value to all the name types as appropriate.