Recognize versions of timestamps with 'T' as the date/time separator.
For example, compare:
'2021-08-01 23:14:00-05:00'
'2021-08-01T23:14:00-05:00'
This commit adds support for the second flavor (and it's variations).
The previous fix for PostgreSQL timestamp fields matched fields with and
without timezones, but did not properly parse values from fields that
included the timezone. Now we check for the presence of the timezone in
the date string and choose a format string to parse it correctly.
