@Bean
	public MessageConverter rocketMQCustomMessageConverter() {
		return new RocketMQMessageConverter();
	}
Register message converter to adapte Spring Cloud Stream.
Refer to https://docs.spring.io/spring-cloud-stream/docs/current/reference/html/spring-cloud-stream.html#spring-cloud-stream-overview-user-defined-message-converters .
@return message converter.
spring-cloud-alibaba-starters/spring-cloud-starter-stream-rocketmq/src/main/java/com/alibaba/cloud/stream/binder/rocketmq/autoconfigurate/ExtendedBindingHandlerMappingsProviderConfiguration.java