Resolve "Duplicating activity do not create new contentId for the contents inside"

Closes #243 (closed)

src/shared/services/graph/node.service.ts

@@ -296,6 +296,7 @@ export function duplicatePage(pageId?: string): void {
         const newElement = JSON.parse(JSON.stringify(elements));
         newElement.id = generateId();
         newElement.parentId = nodeId;
+        newElement.contentId = generateContentId();
         newElements.push(newElement);
     }