Community: add modified_since argument to O365BaseLoader (#28708)

## What are we doing in this PR
We're adding `modified_since` optional argument to `O365BaseLoader`.
When set, O365 loader will only load documents newer than
`modified_since` datetime.

## Why?
OneDrives / Sharepoints can contain large number of documents. Current
approach is to download and parse all files and let indexer to deal with
duplicates. This can be prohibitively time-consuming. Especially when
using OCR-based parser like
[zerox](fa06188834/libs/community/langchain_community/document_loaders/pdf.py (L948)).
This argument allows to skip documents that are older than known time of
indexing.

_Q: What if a file was modfied during last indexing process?
A: Users can set the `modified_since` conservatively and indexer will
still take care of duplicates._




If no one reviews your PR within a few days, please @-mention one of
baskaryan, efriis, eyurtsev, ccurme, vbarda, hwchase17.

---------

Co-authored-by: Erick Friis <erick@langchain.dev>

libs/community/langchain_community/document_loaders/base_o365.py

@@ -9,6 +9,7 @@ import re
 import tempfile
 import urllib
 from abc import abstractmethod
+from datetime import datetime
 from pathlib import Path, PurePath
 from typing import TYPE_CHECKING, Any, Dict, Iterable, List, Optional, Sequence, Union
 
@@ -86,6 +87,9 @@ class O365BaseLoader(BaseLoader, BaseModel):
     """Number of bytes to retrieve from each api call to the server. int or 'auto'."""
     recursive: bool = False
     """Should the loader recursively load subfolders?"""
+    modified_since: Optional[datetime] = None
+    """Only fetch documents modified since given datetime. The datetime object
+    must be timezone aware."""
     handlers: Optional[Dict[str, Any]] = {}
     """
     Provide custom handlers for MimeTypeBasedParser.
@@ -188,6 +192,9 @@ class O365BaseLoader(BaseLoader, BaseModel):
             for file in items:
                 if file.is_file:
                     if file.mime_type in list(file_mime_types.values()):
+                        if (not self.modified_since) or (
+                            file.modified > self.modified_since
+                        ):
                             source = file.web_url
                             if re.search(
                                 r"Doc.aspx\?sourcedoc=.*file=([^&]+)", file.web_url