Change timesheet approver when user's manager is changed

Currently, when you change a user's manager, the approvers set on their existing timesheets are not updated. Sure - all new timesheets will be created with the new manager as the approver, but all the existing timesheets don't get updated and this causes issues as it is easily overlooked.

It would be much better to have all existing timesheet approvers updated when the manager is changed (if the timesheet profile is set for manager approval).