feat(user-creator-chat): WebSocket 메시지 계약을 추가한다

src/main/kotlin/kr/co/vividnext/sodalive/v2/usercreatorchat/websocket/UserCreatorChatWebSocketMessage.kt

@@ -0,0 +1,22 @@
+package kr.co.vividnext.sodalive.v2.usercreatorchat.websocket
+
+import com.fasterxml.jackson.databind.JsonNode
+
+data class UserCreatorChatWebSocketMessage(
+    val type: UserCreatorChatWebSocketMessageType,
+    val requestId: String?,
+    val roomId: Long,
+    val payload: JsonNode
+)
+
+enum class UserCreatorChatWebSocketMessageType {
+    JOIN_ROOM,
+    SEND_TEXT,
+    LEAVE_ROOM,
+    PING,
+    JOINED,
+    MESSAGE,
+    SEND_ACK,
+    ERROR,
+    PONG
+}