fix: issue2551278 - datetime.datetime.utcnow deprecation. We now use the timezone aware utc dates for python 3.11+. But we have to make all the rest of the dates (datetime.min, unix epoch date) timezon aware so we can subtract them. Also need to marshall/unmarshall timezone aware iso formatted date strings.

# https://issues.roundup-tracker.org/issue2551278
# datetime.utcnow deprecated
try:
    from datetime import datetime, UTC

    def utcnow():
        return datetime.now(UTC)

except ImportError:
    from datetime import datetime

    def utcnow():
        return datetime.utcnow()