Set the task due date rule

Sets the single due date rule for a task on a draft workflow revision, replacing any existing rule. Send rule: null (or omit the field) to clear the existing rule. Due date rules cannot be set on headings, AI tasks, or Code tasks — but clearing is always permitted so stale rules left over from prior task edits can be removed. sourceWidgetId is required when sourceType is FormFieldValue and must reference a Date form field widget in the same revision. sourceTaskId is required when sourceType is TaskCompletedDate or TaskDueDate; it must reference a task earlier than the target task in the same revision and cannot be the target task itself. Returns the resulting rule.