public ServerBuilder http2InitialConnectionWindowSize(int http2InitialConnectionWindowSize) {
        checkArgument(http2InitialConnectionWindowSize > 0,
                      "http2InitialConnectionWindowSize: %s (expected: > 0)",
                      http2InitialConnectionWindowSize);
        this.http2InitialConnectionWindowSize = http2InitialConnectionWindowSize;
        return this;
    }
Sets the initial connection-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#defaultHttp2InitialConnectionWindowSize()}.
Note that this setting affects the connection-level window size, not the window size of streams.

@see #http2InitialStreamWindowSize(int)
core/src/main/java/com/linecorp/armeria/server/ServerBuilder.java