Require setting the session timezone to UTC

[Mandukhai-Alimaa]

MySQL converts TIMESTAMP values from the current time zone to UTC for storage, and back from UTC to the current time zone for retrieval and returns a string with no timezone marker. To make sure the timestamp sent and received is consistent, session timezone should be UTC

[lidavidm]

As discussed in the PR I think it would be best to require setting the session timezone to UTC