히스토리 서버 저장 안되는 에러 수정

src/backend/chat_server/build.gradle

@@ -51,9 +51,6 @@ dependencies {
     implementation 'org.springframework.kafka:spring-kafka'
     testImplementation 'org.springframework.kafka:spring-kafka-test'
 
-    //Gson
-    implementation group: 'com.google.code.gson', name: 'gson', version: '2.8.6'
-
     implementation 'org.springframework.boot:spring-boot-starter-data-redis'
 
     annotationProcessor "org.springframework.boot:spring-boot-configuration-processor"

src/backend/chat_server/src/main/java/com/jootalkpia/chat_server/service/KafkaConsumer.java

@@ -40,7 +40,7 @@ public void processMinutePrice(String kafkaMessage) {
 
     @KafkaListener(
             topics = "${topic.chat}",
-            groupId = "${group.chat}", //추후 그룹 ID에 동적인 컨테이너 ID 삽입
+            groupId = "${group.chat}",
             concurrency = "2"
     )
     public void processChatMessage(@Header(KafkaHeaders.RECEIVED_KEY) String channelId, String kafkaMessage) {

src/backend/history_server/src/main/java/com/jootalkpia/history_server/domain/ChatMessage.java

@@ -8,7 +8,7 @@
 
 @Getter
 @Builder
-@Document(collation = "chat_messages")
+@Document(collection = "chat_messages")
 public class ChatMessage extends BaseTimeEntity  {
 
     @Id