Support configuring http2_max_pending_accept_reset_streams

Start at the gRPC server builder's existing HTTP/2 configuration methods and the Http2Config definition. Trace the configuration into the Hyper server setup, then verify that the new option is forwarded and that the default behavior remains unchanged.

Background

The underlying hyper/h2 implementation already supports configuring
http2_max_pending_accept_reset_streams, but this option is currently not
exposed by Volo's gRPC server.

In our production environment, we frequently observe the following warning:

recv_reset; remotely-reset pending-accept streams reached limit (20)

Representative logs:

{"timestamp":"2026-07-15T10:13:08.670091417+08:00","level":"WARN","fields":{"message":"recv_reset; remotely-reset pending-accept streams reached limit (20)"},"target":"h2::proto::streams::recv"}

{"timestamp":"2026-07-15T10:13:08.682643952+08:00","level":"WARN","fields":{"message":"recv_reset; remotely-reset pending-accept streams reached limit (20)"},"target":"h2::proto::streams::recv"}

{"timestamp":"2026-07-15T10:13:08.758969319+08:00","level":"WARN","fields":{"message":"recv_reset; remotely-reset pending-accept streams reached limit (20)"},"target":"h2::proto::streams::recv"}

These warnings are repeatedly emitted under load, indicating that the default
limit (20) is insufficient for some workloads.

Reference

Hyper exposes this configuration because of the discussion in:

https://github.com/hyperium/hyper/issues/2877

Proposed API

Expose the configuration through the gRPC server builder, similar to the
existing HTTP/2 configuration methods.

pub fn http2_max_pending_accept_reset_streams(
    mut self,
    max: impl Into<Option<usize>>,
) -> Self {
    self.http2_config.max_pending_accept_reset_streams = max.into();
    self
}

Store the value in Http2Config:

pub(crate) max_pending_accept_reset_streams: Option<usize>,

with the default value:

max_pending_accept_reset_streams: None,

Finally, propagate the configuration into Hyper:

server
    .http2()
    // ...
    .max_pending_accept_reset_streams(
        self.http2_config.max_pending_accept_reset_streams,
    );

Benefits

• Allows applications to tune the limit for workloads with frequent HTTP/2 stream resets.
• Keeps the current behavior unchanged by default.
• Aligns Volo with the underlying Hyper API.
• The implementation is straightforward and fully backward compatible.