Add a hyper client implementation

[bspeice]

Given http-rs/async-h1#109, I don't think it's possible to add tokio as an executor for async-h1. Instead, we can add hyper as a client to the http-client facade, allowing for libraries built on top of http-client to be executor independent.

I still need to do come cleanup and testing, but I wanted to present the work thus far and ask:

• Is this organization interested in supporting a tokio-based client?
• If so, I could use some help clarifying some behavior (the most interesting bits are in HttpTypesResponse::try_from())

[bspeice]

Also, opened the PR before noticing #1, but this should fix it.

[yoshuawuyts]

Is this organization interested in supporting a tokio-based client?

I definitely am! -- I've had frustrating experiences with Hyper and Tokio in the past, to the point that I found it easier to work on a new HTTP stack and runtime. But if this is something that you'd be willing to implement and maintain, then it's most definitely welcome!

[bspeice]

Glad to hear. I have some other libraries I'm working on, and the goal is to make sure that there's meaningful cross-executor support. Happy to help maintain this, I'll get it cleaned up this morning and post another comment once it's ready for a more thorough inspection.

[bspeice]

This is ready for review once a maintainer has availability.

[yoshuawuyts]

http-types has a hyperium-http feature that implements most of the conversions in this PR for you.

An overview of the conversions is here. I believe this covers most of it, but if we're missing something we can update http-types. That should cover some of the gnarlier bits of this PR (:

[bspeice]

My concern with hyperium-http was that it would be enabled unconditionally. There's a nightly Cargo feature to conditionally enable features, but right now, adding hyperium-http means that all users (even those who don't use the hyper client) would need to compile the http crate. By re-implementing the conversions from hyper types (which are largely re-exports of http), you only compile http when necessary.

Long story short - happy to use hyperium-http and take advantage of the conversions, but there is a compile-time penalty for all non-hyper users.

[bspeice]

Minor note after conversion: the header conversion functions aren't public and because of body type mis-matches they can't be accessed as part of the From<> conversions.

[bspeice]

Just wanted to check - is there anything else that needs to be done here? To the best of my knowledge, this is ready for review/merge.

[yoshuawuyts]

This looks great; thanks so much!