Update therapy session table to handle null & fix issue with session completion #293

This will handle the case where simplybook does not send timezone information for a booking. This happens when the therapist makes the booking on the client's behalf. The client timezone is not available in this case. It is always available when the client makes their own booking. d0ee58e1b8 / Handle empty timezone in simplybook webhook

d0ee58e1b8 / Handle empty timezone in simplybook webhook