It seems that customer sync only works for customer creation and payment related tasks, but customer accounts created in stripe via lago synchronization are not deleted when the customer is deleted in Lago. Lago should check with the payment provider if all due payments are finalized (or void), and if so, it should delete the customer in Stripe. Likewise, when a customer is deleted in Lago but still has invoices to pay, Lago should sync the user deletion when these invoices are finalized or void.