Need to set content-type for certain cluster types

[clux]

From reports on discord, https://agones.dev/site/ does require the content-type header set, and we are not setting it.

• We probably need to incorporate this into a new layer or our base layer.
• We might need to make this configurable in the future to handle protobufs

But we can work around this with tower-http middleware:

async fn build_kube_client(namespace: &str) -> Result<Client, AgonesError> {
    let config = Config::infer().await?;
    let https = config.rustls_https_connector()?;

    let service = tower::ServiceBuilder::new()
        // required setup for `kube::Client` to work
        .layer(config.base_uri_layer())
        .option_layer(config.auth_layer()?)
        // kube doesn't set `content-type: application/json` which agones requires
        .layer(SetRequestHeaderLayer::<_, Body>::if_not_present(
            http::header::CONTENT_TYPE,
            http::HeaderValue::from_static("application/json"),
        ))
        .service(hyper::Client::builder().build(https));

    Ok(Client::new(service, namespace))
}

Via discord

[nightkr]

Seems like this would belong in our Request creation code, since the content-type already has semantic significance for patches?

[clux]

Seems like this would belong in our Request creation code, since the content-type already has semantic significance for patches?

That is true! We can tie it to our Request by using the setters on http::Request (instead of hard-overriding it with layers) and then we tie the content type to the http api explicitly.

[kazk]

Opened #627