Model
CreditmemoNotifier
Magento\Sales\Model\Order\CreditmemoNotifier
What it does
The CreditmemoNotifier class is responsible for sending credit memo email notifications to customers when a refund is processed.
Developers would use this class when they need to programmatically trigger credit memo notification emails after creating or updating a credit memo in Magento 2.
It extends AbstractNotifier and uses the CreditmemoSender to handle the actual email delivery.