BOR / Reg Search - Update utcnow to func.now() in the model

The func.now() function will set the default datetimes to the start of the session (this will be the start of the request), which is what we want.
One known issue is that for the tests the session is set at the beginning of the test setup so we will need to look into changing how those tests work (i.e. the default time in the tests will not accurately reflect actual functionality when this is updated)

Start by locating the BOR / Reg Search model fields that currently use utcnow and the tests covering their default datetimes. Review how the test session is initialized, then update the model defaults and adjust the tests so they verify the session-start time behavior described in the issue.

Written by the indexing model from the issue text.