Authorization for cancelling an order is different for matching an order#

The cancel function simply requires require(_msgSender() == order.maker, "not a maker"); for cancelling an order.

However orders can be authorized with matchOrders by using _msgSender() == order.maker or signatures from users or signatures from contracts.

So orders that are started with matchOrders using signatures can't be cancelled using signatures.

However this is fine if this is the desired functionality.