fix: Referencing Metadata in the response of the External Knowledge A… (#19637) (#19644)

Co-authored-by: satou.kazuhiro <satou.kazuhiro@fanuc.co.jp>

api/core/workflow/nodes/knowledge_retrieval/knowledge_retrieval_node.py

@@ -264,6 +264,7 @@ class KnowledgeRetrievalNode(LLMNode):
                     "data_source_type": "external",
                     "retriever_from": "workflow",
                     "score": item.metadata.get("score"),
+                    "doc_metadata": item.metadata,
                 },
                 "title": item.metadata.get("title"),
                 "content": item.page_content,