feat(http2): add initial_max_send_streams method to HTTP/2 client builder (#3524)

Author: magurotuna

Diff for: src/client/conn/http2.rs

@@ -305,6 +305,19 @@ where
         self
     }
 
+    /// Sets the initial maximum of locally initiated (send) streams.
+    ///
+    /// This value will be overwritten by the value included in the initial
+    /// SETTINGS frame received from the peer as part of a [connection preface].
+    ///
+    /// The default value is determined by the `h2` crate, but may change.
+    ///
+    /// [connection preface]: https://httpwg.org/specs/rfc9113.html#preface
+    pub fn initial_max_send_streams(&mut self, initial: impl Into<Option<usize>>) -> &mut Self {
+        self.h2_builder.initial_max_send_streams = initial.into();
+        self
+    }
+
     /// Sets whether to use an adaptive flow control.
     ///
     /// Enabling this will override the limits set in

Diff for: src/proto/h2/client.rs

@@ -57,6 +57,7 @@ pub(crate) struct Config {
     pub(crate) adaptive_window: bool,
     pub(crate) initial_conn_window_size: u32,
     pub(crate) initial_stream_window_size: u32,
+    pub(crate) initial_max_send_streams: Option<usize>,
     pub(crate) max_frame_size: u32,
     pub(crate) keep_alive_interval: Option<Duration>,
     pub(crate) keep_alive_timeout: Duration,
@@ -71,6 +72,7 @@ impl Default for Config {
             adaptive_window: false,
             initial_conn_window_size: DEFAULT_CONN_WINDOW,
             initial_stream_window_size: DEFAULT_STREAM_WINDOW,
+            initial_max_send_streams: None,
             max_frame_size: DEFAULT_MAX_FRAME_SIZE,
             keep_alive_interval: None,
             keep_alive_timeout: Duration::from_secs(20),
@@ -89,6 +91,9 @@ fn new_builder(config: &Config) -> Builder {
         .max_frame_size(config.max_frame_size)
         .max_send_buffer_size(config.max_send_buffer_size)
         .enable_push(false);
+    if let Some(initial_max_send_streams) = config.initial_max_send_streams {
+        builder.initial_max_send_streams(initial_max_send_streams);
+    }
     if let Some(max) = config.max_concurrent_reset_streams {
         builder.max_concurrent_reset_streams(max);
     }