Function accepted_stream 

pub fn accepted_stream(
    send: SendStream,
    recv: RecvStream,
    frame_limit: usize,
    progress_timeout: Duration,
    method: &MethodDescriptor,
) -> Result<(Writer, Reader), Error>

Adapt an already accepted RPC stream after the caller parsed its bounded request prelude. This performs framing only; the server must independently authorize the exact opening before admission or disclosure.