Http2 client configuration to improve performance (#1394)

* add defaults for http2 client configuration

* fix spaces

* Add changes text for extended H2 defaults buffers

* client: configurable H2 window sizes and max_http_version

* add H2 window size configuration and max_http_version to awc::ClientBuilder

* add awc::ClientBuilder H2 window sizes and max_http_version

* add test for H2 window size settings

* cleanup comment

* Apply code review fixes

* Code review fix for awc ClientBuilder

* Remove unnecessary comments on code review

* pin quote version to resolve build issue

* max_http_version to accept http::Version

* revert fix for quote broken build

awc/tests/test_connector.rs

@@ -0,0 +1,61 @@
+#![cfg(feature = "openssl")]
+use actix_http::HttpService;
+use actix_http_test::test_server;
+use actix_service::{map_config, ServiceFactory};
+use actix_web::http::Version;
+use actix_web::{dev::AppConfig, web, App, HttpResponse};
+use open_ssl::ssl::{SslAcceptor, SslConnector, SslFiletype, SslMethod, SslVerifyMode};
+
+fn ssl_acceptor() -> SslAcceptor {
+    // load ssl keys
+    let mut builder = SslAcceptor::mozilla_intermediate(SslMethod::tls()).unwrap();
+    builder
+        .set_private_key_file("../tests/key.pem", SslFiletype::PEM)
+        .unwrap();
+    builder
+        .set_certificate_chain_file("../tests/cert.pem")
+        .unwrap();
+    builder.set_alpn_select_callback(|_, protos| {
+        const H2: &[u8] = b"\x02h2";
+        if protos.windows(3).any(|window| window == H2) {
+            Ok(b"h2")
+        } else {
+            Err(open_ssl::ssl::AlpnError::NOACK)
+        }
+    });
+    builder.set_alpn_protos(b"\x02h2").unwrap();
+    builder.build()
+}
+
+#[actix_rt::test]
+async fn test_connection_window_size() {
+    let srv = test_server(move || {
+        HttpService::build()
+            .h2(map_config(
+                App::new().service(
+                    web::resource("/").route(web::to(|| HttpResponse::Ok())),
+                ),
+                |_| AppConfig::default(),
+            ))
+            .openssl(ssl_acceptor())
+            .map_err(|_| ())
+    });
+
+    // disable ssl verification
+    let mut builder = SslConnector::builder(SslMethod::tls()).unwrap();
+    builder.set_verify(SslVerifyMode::NONE);
+    let _ = builder
+        .set_alpn_protos(b"\x02h2\x08http/1.1")
+        .map_err(|e| log::error!("Can not set alpn protocol: {:?}", e));
+
+    let client = awc::Client::build()
+        .connector(awc::Connector::new().ssl(builder.build()).finish())
+        .initial_window_size(100)
+        .initial_connection_window_size(100)
+        .finish();
+
+    let request = client.get(srv.surl("/")).send();
+    let response = request.await.unwrap();
+    assert!(response.status().is_success());
+    assert_eq!(response.version(), Version::HTTP_2);
+}