fix: 엔티티 생성시간 자동 기입 기능 추가 (#63) (KAN-114)

src/main/java/org/ioteatime/meonghanyangserver/group/domain/GroupEntity.java

@@ -8,13 +8,16 @@
 import lombok.Data;
 import lombok.NoArgsConstructor;
 import org.ioteatime.meonghanyangserver.device.doamin.DeviceEntity;
+import org.springframework.data.annotation.CreatedDate;
+import org.springframework.data.jpa.domain.support.AuditingEntityListener;
 
 @Data
 @Entity
 @NoArgsConstructor
 @AllArgsConstructor
 @Builder
 @Table(name = "`group`")
+@EntityListeners(AuditingEntityListener.class)
 public class GroupEntity {
     @Id
     @GeneratedValue(strategy = GenerationType.IDENTITY)
@@ -23,8 +26,7 @@ public class GroupEntity {
     @Column(nullable = false, length = 100)
     private String groupName;
 
-    @Column(nullable = false)
-    private LocalDateTime createdAt;
+    @Column @CreatedDate private LocalDateTime createdAt;
 
     @OneToMany(mappedBy = "group")
     private List<DeviceEntity> deviceEntities;