Replace reqwest with hyper + tower

[kazk]

Replace reqwest with hyper (#362) and tower (#100). Supersedes #376.

Changes

kube::Client now uses kube::Service instead of reqwest::Client

 #[derive(Clone)]
 pub struct Client {
-    cluster_url: reqwest::Url,
-    default_ns: String,
-    inner: reqwest::Client,
-    config: Config,
-    #[cfg(feature = "ws")]
-    tls_connector: AsyncTlsConnector,
+    inner: kube::Service,
 }

kube::Service struct is a tower::Service<http::Request<hyper::Body>>. For convenience, a service based on hyper::Client can be created from kube::Config, so Client::try_default() is still supported. We can add a feature for this to provide an option for a sans-io Client (#204).

To allow users to use their implementation when they need something not supported out of the box, I'm planning to change Client::new(config: Config) to Client::new(service: Service) (creating a Client from Config is still possible with Client::new(config.try_into()?)). This will also allow better testing.

kube::Service uses tower::buffer::Buffer, so it's cheap to clone (#17).

Upgrade to WebSocket connection with hyper

The above change was possible because of this. No more separate client for WebSocket! The connection is upgraded with hyper and a WebSocketStream is created from the upgraded connection. All requests go through kube::Service.

Other Improvements

• Rewrote Client::request_events with tokio_util::codec::FramedRead (Factor out chunked reader from Client::request_events #379)
• Refactored TLS related code. It's now all isolated in kube/src/service/tls.rs. kube/src/config/auth.rs has HttpsConnector for oauth requests and kube/src/config/mod.rs has some hack for macOS, but that's about it.
• Replaced oauth2 (GCP OAuth) module with tame-oauth and made it optional (oauth feature).
• Refactored auth related code and moved them to config::auth.
• Fixed a bug where refreshable token from AuthProvider was not refreshing.
• Fixed panicking when loading AuthInfo with provider other than GCP (Panic when creating Config object with Azure provider #238).

Breaking Changes

• oauth is now opt-in
• gzip should probably be opt-in for now because Kubernetes doesn't have it enabled by default yet and requires more dependencies. It's behind APIResponseCompression feature gate which is in Beta since 1.16. See https://kubernetes.io/docs/reference/command-line-tools-reference/feature-gates/.
• TODO Change kube::Client::new(config: Config) to kube::Client::new(service: Service)
• Dropped proxy option. It should be possible by using a custom Service after the above change. TODO add example.

---

Closes #100, #238, #362, #379

[kazk]

This can be used for a (hacky) solution for #209 by adding a placeholder in Api then replacing it with default_ns before making a request.

pub fn default_namespaced(client: Client) -> Self {
    let resource = Resource::namespaced::<K>("{{default_ns}}");
    Self {
        resource,
        client,
        phantom: iter::empty(),
    }
}

let inner = ServiceBuilder::new()
    .map_request(move |r| finalize_url(r, &url, &default_ns))
    .service(client);

[clux]

Hah, that is actually a pretty good solution. The braces would mean we cannot clash with an actual namespace.

[clux]

Looks really good, once again (original pr already had a significant amount of iteration). Everything is very cleanly done, modules delineated a lot better than before.
Less dependency multiplicity now that everything goes through the same service.
Have tested it a bit on your branch, and don't see any issues either, it just works. ✨

Happy to merge so we can rebase the remaining PRs (rather than the other way around).

[kazk]

Thanks for reviewing and testing. Glad to hear it just worked ✨
I haven't found any issues running the examples either. Let's merge it 👍
I'll open separate PRs for any follow-ups. This is already too big.

[clux]

Awesome. It's going in! Thank you so much for digging into all of this (and effectively rewriting both the client and the config). This is a huge improvement.

I'll open separate PRs for any follow-ups. This is already too big.
Agreed, it snowballed :D
But all good.

[clux]

Added some basic info about this in the CHANGELOG. Feel free to update as you see fit.

Want me to wait with making a release until any of the follow-up tasks?

• gzip opt-in (agreed if it's not default in kubernetes)
• kube::Client From Service

The last one would good for the sans-io story, even if it's only for us being able to provide a better testing. (Not sure there are any people masochistic enough to want to change out the full client stack, but maybe I am wrong).

[kazk]

Opened #399 (gzip), #400 (Client::new), #401 (fix docs), and #402 (changelog).

[clux]

wow that was a lot of prs in one night, thanks a lot.
i have merged them all. i'll push out a minor release now.

[clux]

All of it released in 0.49.0 ✨