Moves a phase to a new start date and moves its assignments by the same number of weekdays, keeping each assignment's own weekday length. Assignments marked as non-working days stay where they are, and actuals are never moved. The whole move is applied in one transaction, so either every date changes or none does. To change a phase's dates without touching its assignments, use PATCH /projects/{projectId}/phases/{phaseId} instead. This endpoint is in limited release and returns 403 for accounts without access. Please contact [email protected] if you'd like to use it.