Implement AsRef<[u8]> for Binary/HexBinary

[webmaster128]

needed for hashers like sha2::Sha256::digest(

[ethanfrey]

It's not there? We have something (Deref?)

I have passed &bin into a function expecting &[u8] when bin: Binary.

[webmaster128]

Turns out we can use an as_ref function because of the Deref implemenation. But since the AsRef<[u8]> trait bound was not satisfied, our type could not be used in places that require impl AsRef<[u8]> as an argument.

[webmaster128]

I have passed &bin into a function expecting &[u8]

Right, there we have no issues. But this is for functions that take impl AsRef<[u8]> arguments, like this one: https://docs.rs/sha2/0.10.6/sha2/trait.Digest.html#tymethod.digest