[community] [Bugfix] base_o365 document loader metadata needs to be J…

…SON serializable (#26322)

In order for indexer to work, all metadata in the documents need to be
JSON serializable. Timestamps are not.

See here:

https://github.com/langchain-ai/langchain/blob/master/libs/core/langchain_core/indexing/api.py#L83-L89

@eyurtsev could you please review? It's a tiny PR :-)

libs/community/langchain_community/document_loaders/base_o365.py

@@ -118,8 +118,8 @@ def _load_from_folder(self, folder: Folder) -> Iterable[Blob]:
                         metadata_dict[file.name] = {
                             "source": file.web_url,
                             "mime_type": file.mime_type,
-                            "created": file.created,
-                            "modified": file.modified,
+                            "created": str(file.created),
+                            "modified": str(file.modified),
                             "created_by": str(file.created_by),
                             "modified_by": str(file.modified_by),
                             "description": file.description,