[AB-71] adding cache flag to cached message

abstracto-application/core/core-int/src/main/java/dev/sheldan/abstracto/core/models/cache/CachedAttachment.java

@@ -14,6 +14,7 @@ public class CachedAttachment implements Serializable {
     private Long id;
     private String proxyUrl;
     private String fileName;
+    private Boolean spoiler;
     private Integer size;
     private Integer height;
     private Integer width;