feat: support non utf8 strings

[omjadas]

fixes #59
Allows non UTF-8 values to be used for distinguished name entries

[est31]

Thanks for the PR! This is an API breaking change, so requires a minor semver bump for a future release. Not sure yet if I want to wait with merging or merge it right now.

[est31]

I'd prefer to keep the old API for the push side, as 99% of use cases would probably be UTF-8 strings. This doesn't just reduce the diff of this PR but also makes updating easier for the users. Usage of the API would also remain as easy as it used to be. Can you rename this function to push_ext or something and say something along the lines that you should use push unless there is a specific need to use something other than Utf8Strings?

The get side is fine, as I think it's less used.

[omjadas]

Would it be better to have a single method that takes an impl Into<DnValue> and provide the following implementation?

impl<T> From<T> for DnValue
where
	T :Into<String>
{
	fn from(t :T) -> Self {
		DnValue::Utf8String(t.into())
	}
}

[est31]

Would it be better to have a single method that takes an impl Into and provide the following implementation?

That's a great idea! I'm a bit worried though that the impl is not immediately seen. A code example in the rustdoc that uses a str literal would solve that I think.

[omjadas]

@est31 I have updated the PR per your suggestions. Let me know if you would prefer push to be split into separate methods and I can make the change.

[est31]

Also I'd like to see a test case for #59. Ideally it'd not use a certificate from the wild due to copyright but one you generated yourself (maybe even using rcgen). As for the breaking change, one of the possible resolutions of #65 seems to require one already, and the ring author said they wanted to make a breaking change themselves soon.

[omjadas]

@est31 I have added the requested example and tests. Let me know if there is anything else you would like changed/added.

[est31]

OK except for nits.