docs:
https://docs.spring.io/spring-framework/docs/5.0.4.RELEASE/spring-framework-reference/web.html#websocket-stomp-message-flow
일반 WebSocket 정리
https://brunch.co.kr/@springboot/695
https://m.blog.naver.com/PostView.naver?isHttpsRedirect=true&blogId=scw0531&logNo=221097188275