static WebSocketClientBuilder builder(String scheme, EndpointGroup endpointGroup) {
        requireNonNull(scheme, "scheme");
        return builder(Scheme.parse(scheme), endpointGroup);
    }
Returns a new {@link WebSocketClientBuilder} created with the specified {@code scheme}
and the {@link EndpointGroup}.
core/src/main/java/com/linecorp/armeria/client/websocket/WebSocketClient.java