@Override
    @Deprecated
    public WebSocketClientBuilder preprocessor(HttpPreprocessor preprocessor) {
        throw new UnsupportedOperationException("WebSocketClientBuilder does not support preprocessor.");
    }
Raises an {@link UnsupportedOperationException} because {@link WebSocketClient} does
not support {@link HttpPreprocessor}.

@deprecated HTTP preprocessor cannot be added to the {@link WebSocketClient}.
core/src/main/java/com/linecorp/armeria/client/websocket/WebSocketClientBuilder.java