fix: Fixed BaseTimeEntity class

- added @MappedSuperClass
- added @column(updatable=false) to createdDate field

closes #11

src/main/java/com/f_lab/la_planete/domain/base/BaseTimeEntity.java

@@ -1,16 +1,20 @@
 package com.f_lab.la_planete.domain.base;
 
+import jakarta.persistence.Column;
 import jakarta.persistence.EntityListeners;
+import jakarta.persistence.MappedSuperclass;
 import org.springframework.data.annotation.CreatedDate;
 import org.springframework.data.annotation.LastModifiedDate;
 import org.springframework.data.jpa.domain.support.AuditingEntityListener;
 
 import java.time.LocalDateTime;
 
+@MappedSuperclass
 @EntityListeners(AuditingEntityListener.class)
 public abstract class BaseTimeEntity {
 
   @CreatedDate
+  @Column(updatable = false)
   private LocalDateTime createdAt;
   @LastModifiedDate
   private LocalDateTime modifiedAt;