feat: builder with shared configuration

Sometimes one might want to share the config to the builder api like one can to the connector api itself, allowing some optimization.

Since the config eventually get's `Arc`-d anyways there can be no disadvantage to this.

src/connector/builder.rs

@@ -1,3 +1,5 @@
+use std::sync::Arc;
+
 use hyper_util::client::legacy::connect::HttpConnector;
 #[cfg(any(feature = "rustls-native-certs", feature = "webpki-roots"))]
 use rustls::crypto::CryptoProvider;
@@ -44,6 +46,27 @@ impl ConnectorBuilder<WantsTlsConfig> {
     /// [`enable_http2`](ConnectorBuilder::enable_http2)) before the
     /// connector is built.
     pub fn with_tls_config(self, config: ClientConfig) -> ConnectorBuilder<WantsSchemes> {
+        assert!(
+            config.alpn_protocols.is_empty(),
+            "ALPN protocols should not be pre-defined"
+        );
+        ConnectorBuilder(WantsSchemes {
+            tls_config: Arc::new(config),
+        })
+    }
+
+    /// Passes an [`Arc`]-shared rustls [`ClientConfig`] to configure the TLS connection
+    ///
+    /// The [`alpn_protocols`](ClientConfig::alpn_protocols) field is
+    /// required to be empty (or the function will panic) and will be
+    /// rewritten to match the enabled schemes (see
+    /// [`enable_http1`](ConnectorBuilder::enable_http1),
+    /// [`enable_http2`](ConnectorBuilder::enable_http2)) before the
+    /// connector is built.
+    pub fn with_shared_tls_config(
+        self,
+        config: Arc<ClientConfig>,
+    ) -> ConnectorBuilder<WantsSchemes> {
         assert!(
             config.alpn_protocols.is_empty(),
             "ALPN protocols should not be pre-defined"
@@ -133,7 +156,7 @@ impl Default for ConnectorBuilder<WantsTlsConfig> {
 /// State of a builder that needs schemes (https:// and http://) to be
 /// configured next
 pub struct WantsSchemes {
-    tls_config: ClientConfig,
+    tls_config: Arc<ClientConfig>,
 }
 
 impl ConnectorBuilder<WantsSchemes> {
@@ -166,7 +189,7 @@ impl ConnectorBuilder<WantsSchemes> {
 ///
 /// No protocol has been enabled at this point.
 pub struct WantsProtocols1 {
-    tls_config: ClientConfig,
+    tls_config: Arc<ClientConfig>,
     https_only: bool,
     override_server_name: Option<String>,
 }
@@ -176,7 +199,7 @@ impl WantsProtocols1 {
         HttpsConnector {
             force_https: self.https_only,
             http: conn,
-            tls_config: std::sync::Arc::new(self.tls_config),
+            tls_config: self.tls_config,
             override_server_name: self.override_server_name,
         }
     }