Log post visibility changes

backend/src/main/java/com/openisle/model/PostChangeType.java

@@ -8,6 +8,7 @@ public enum PostChangeType {
   CLOSED,
   PINNED,
   FEATURED,
+  VISIBLE_SCOPE,
   VOTE_RESULT,
   LOTTERY_RESULT,
   DONATE,

backend/src/main/java/com/openisle/model/PostVisibleScopeChangeLog.java

@@ -0,0 +1,23 @@
+package com.openisle.model;
+
+import jakarta.persistence.Entity;
+import jakarta.persistence.EnumType;
+import jakarta.persistence.Enumerated;
+import jakarta.persistence.Table;
+import lombok.Getter;
+import lombok.NoArgsConstructor;
+import lombok.Setter;
+
+@Getter
+@Setter
+@NoArgsConstructor
+@Entity
+@Table(name = "post_visible_scope_change_logs")
+public class PostVisibleScopeChangeLog extends PostChangeLog {
+
+  @Enumerated(EnumType.STRING)
+  private PostVisibleScopeType oldVisibleScope;
+
+  @Enumerated(EnumType.STRING)
+  private PostVisibleScopeType newVisibleScope;
+}