Gmail connector fails to index on malformed date strings

[sam-w]

Email is not great - it's pretty common to see malformed date strings of the form <datetime> +<tz offset> (<invalid tz name>) in the Date header field, as returned by the Gmail API.

Some concrete examples from our Gmail:

• Thu, 23 Jan 2025 11:04:48 +0300 (+03) (DMARC report)
• Sat, 25 Jan 2025 05:15:30 +1100 (AUSNSW) (automated invoice from a partner's legacy system)

These cause Gmail connector indexing to fail on this line. dateutil.parse doesn't know how to parse those strings because it's expecting the timezone name (in parentheses) to be < 5 characters and composed only of uppercase ASCII.

The gmail connector needs some way to handle these almost-ok-but-still-invalid date strings.