Add support for hyper-rustls

[wezm]

Description

Allow the hyper client to be configured to use hyper-rustls for TLS abilities, eliminating the dependency on the OS TLS library/OpenSSL.

Motivation and Context

Fixes #40

This is a quick pass at using hyper-rustls instead of native-tls. rustls makes cross-compiling easier and eliminates a dependency on a C library (OpenSSL) on open source OSes.

How Has This Been Tested?

These changes build with cargo build --no-default-features --features hyper-client,hyper-rustls,rustls. However, cargo test --no-default-features --features hyper-client,hyper-rustls,rustls fails. It appears that running the tests is broken on master with native-tls too, as cargo test --no-default-features --features hyper-client,hyper-tls,native-tls also fails.

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.
• All new and existing tests passed.

[yoshuawuyts]

@wezm I'm kind of wondering if we shouldn't straight up replace hyper's tls impl with rustls. There's quite a few options possible for hyper and if possible I'd like to prevent a combinatorial explosion in our configs for hyper features. How do you feel about only exposing rustls as Hyper's only TLS impl?

[wezm]

How do you feel about only exposing rustls as Hyper's only TLS impl?

That would be fine with me.

[hirrolot]

@wezm I'm kind of wondering if we shouldn't straight up replace hyper's tls impl with rustls. There's quite a few options possible for hyper and if possible I'd like to prevent a combinatorial explosion in our configs for hyper features. How do you feel about only exposing rustls as Hyper's only TLS impl?

I think that not all users of Surf may want to use Rustls and forget about a native TLS implementation (see the discussion in #40).

[yoshuawuyts]

@Gymmasssorla We should probably make http-client public so any kind of configuration can be created.

[yoshuawuyts]

http-client is public now, and lives as part of a separate crate. We should pick the work in this patch back up there. It's currently being integrated back into Surf; so fingers crossed we can add support for this.

Going to go ahead and close this patch for now, as we can't merge it into this repo anymore. Thanks heaps @wezm for your work!