How can I set the isCompleted status of an order from within a custom module?

Question

The default behaviour for commerce is to mark the isCompleted flag on an order to true once the order has been paid for.

I have need to alter this behaviour and only want to mark an order as Complete via manual intervention of a site admin - or after a predefined date has passed.

Is it possible to set the isCompleted flag from within a custom module? Right now, I'm listening to the EVENT_AFTER_ORDER_PAID then attempting to set the isCompleted flag and save the order.

What I can't figure out is how to save the order!

Code so far, for what it's worth:

Event::on(
            Order::class, 
            Order::EVENT_AFTER_ORDER_PAID, 
            function(Event $e) {
                $order = $e->sender;

                $order->isCompleted = false; // no idea if this is correct

                $order->saveOrder(); // this doesn't work
            }
        );

Answer 1

This can be achieved with

Event::on(
            Order::class, 
            Order::EVENT_AFTER_COMPLETE_ORDER, 
            function(Event $e) {

                $order = $e->sender;

                $order->isCompleted = false;
                Craft::$app->getElements()->saveElement($order, false);

            }
        );

But I'm not sure it's actually a good idea anyway.