Use new headers crate instead of hyper-old-types

[mthebridge]

Signed-off-by: Mark Thebridge mark.thebridge@metaswitch.com

hyper-old-types is no longer maintained. Switch to the headers hyper crate instead - https://docs.rs/headers/latest/headers/authorization/index.html

This is a breaking change because swagger-rs re-exported types.

• Rather than continue to re-export, I've made the AuthData enum variants just wrap Strings. This is slightly uglier, but the inner Basic and Bearer types in headers can't be directly constructed, only decoded from an Authorization header, and this felt like a more efficient implementation.
• The from_headers method now returns an Option<AuthData>, thus removing any public authentication type reexports and avoiding exposing the whole swagger ecosystem to upstream breaking changes.

There were no existing tests of AuthData - not sure what would be useful to add, but will do if there's anything you think would help?

[mthebridge]

I've just realised this is a pretty pointless implementation - I'm cnnstucting the header for no reason. I feel like ideally, we would return https://docs.rs/headers/latest/headers/authorization/struct.Basic.html here - but that has no constructor beyond a decode from a HeaderValue. (Same applies to the Bearer variant). We could make the inner type an authorization header but that feels wrong too.

Thoughts welcome!