public ServerBuilder http2InitialStreamWindowSize(int http2InitialStreamWindowSize) {
        checkArgument(http2InitialStreamWindowSize > 0,
                      "http2InitialStreamWindowSize: %s (expected: > 0)",
                      http2InitialStreamWindowSize);
        this.http2InitialStreamWindowSize = http2InitialStreamWindowSize;
        return this;
    }
Sets the initial stream-level HTTP/2 flow control window size. Larger values can lower stream
warmup time at the expense of being easier to overload the server. Defaults to
{@link Flags#defaultHttp2InitialStreamWindowSize()}.
Note that this setting affects the stream-level window size, not the window size of connections.

@see #http2InitialConnectionWindowSize(int)
core/src/main/java/com/linecorp/armeria/server/ServerBuilder.java