Add post and tag review workflow

src/main/java/com/openisle/model/NotificationType.java

@@ -10,6 +10,8 @@ public enum NotificationType {
     COMMENT_REPLY,
     /** Someone reacted to your post or comment */
     REACTION,
+    /** A new post is waiting for review */
+    POST_REVIEW_REQUEST,
     /** Your post under review was approved or rejected */
     POST_REVIEWED,
     /** A subscribed post received a new comment */

src/main/java/com/openisle/model/Tag.java

@@ -26,4 +26,7 @@ public class Tag {
 
     @Column(name = "description", nullable = false)
     private String description;
+
+    @Column(nullable = false)
+    private boolean approved = true;
 }