Consider using non-rustls types in the API

[Ralith]

In its current form, this library must be updated for every new rustls release. Given the small size and specific responsibilities, removing the rustls dependency would likely allow the library to remain unchanged for much longer periods, reducing maintenance load. As a straw proposal, DER blobs could be returned as Vec<Vec<u8>>.

[djc]

Plus rustls could have like a TryFrom impl for whatever type you use here?

[ctz]

I'll probably need to hoist the PEM code out of rustls to achieve this. But that seems like a good idea.

[Ralith]

This is currently making it difficult to have a git dependency on rustls, which causes problems like quinn-rs/quinn#805.

[est31]

👍 I wanted to use this crate with reqwest's rustls mode and call add_root_certificate but reqwest has its own certificate types which abstract over the various backends, so the rustls types aren't helpful here. I guess reqwest doesn't want to become dependent on the version of rustls so it'll likely not want to expose compatibility with rustls types in the API.

[est31]

#12