Fix #13119: Use email.utils to fix IMAP parsing for names with commas (#13120)

## Type of Change
- [x] Bug fix

## Description
Closes #13119

The current IMAP connector uses `split(',')` to parse email headers,
which crashes when a sender's display name contains a comma inside
quotes (e.g., `"Doe, John" <john@example.com>`).

This PR replaces the manual string splitting with Python's standard
`email.utils.getaddresses`. This correctly handles RFC 5322 quoted
strings and prevents the `RuntimeError: Expected a singular address`.

## Checklist
- [x] I have checked the code and it works as expected.

---------

Co-authored-by: Kevin Hu <kevinhu.sh@gmail.com>

common/data_source/imap_connector.py

@@ -8,7 +8,7 @@ import re
 from datetime import datetime, timedelta
 from datetime import timezone
 from email.message import Message
-from email.utils import collapse_rfc2231_value, parseaddr
+from email.utils import collapse_rfc2231_value, getaddresses
 from enum import Enum
 from typing import Any
 from typing import cast
@@ -617,9 +617,9 @@ def _sanitize_mailbox_names(mailboxes: list[str]) -> list[str]:
 
 
 def _parse_addrs(raw_header: str) -> list[tuple[str, str]]:
-    addrs = raw_header.split(",")
-    name_addr_pairs = [parseaddr(addr=addr) for addr in addrs if addr]
-    return [(name, addr) for name, addr in name_addr_pairs if addr]
+    if not raw_header:
+        return []
+    return getaddresses([raw_header])
 
 
 def _parse_singular_addr(raw_header: str) -> tuple[str, str]:
@@ -721,4 +721,4 @@ if __name__ == "__main__":
         start=START,
         end=END,
     ):
-        print(doc.id,doc.extension)
+        print(doc.id,doc.extension)