Support for borrowing newtypes

[Ducky2048]

First of all, thank you for this library! I like it a lot.

I have a request:

I would like to make newtypes containing borrowed values, but it appears that doesn't work.

For example, this:

#[nutype(derive(Debug))]
struct A<'a>(Cow<'a, str>);

Expands to this:

#[doc(hidden)]
mod __nutype_private_A__ {
    use super::*;

    #[derive(Debug, )]
   /// Lifetime on A is missing
    pub struct A(Cow<'a, str>);

    impl A {
        pub fn new(raw_value: Cow<'a, str>) -> Self {
            fn sanitize(mut value: Cow<'a, str>) -> Cow<'a, str> { value }
            Self(sanitize(raw_value))
        }
    }

    impl A { pub fn into_inner(self) -> Cow<'a, str> { self.0 } }
}
use __nutype_private_A__::A

The important part is that the lifetime declaration on A seems to be lost. Is it possible to make this work?

[greyblake]

Hi, thanks for reporting the issue.
Currently generics are not yet support, but I plan to add support for this.
There is a related issue to this: #130