How does \Magento\OfflinePayments\Observer\BeforeOrderPaymentSaveObserver handle the «sales_order_payment_save_before» event?

Development Payment
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1

Context: How does a payment saving work?

958164/app/code/Magento/OfflinePayments/Observer/BeforeOrderPaymentSaveObserver.php#L19-L48

class BeforeOrderPaymentSaveObserver implements ObserverInterface
{
    /**
     * Sets current instructions for bank transfer account
     *
     * @param \Magento\Framework\Event\Observer $observer
     * @return void
     */
    public function execute(\Magento\Framework\Event\Observer $observer)
    {
        /** @var \Magento\Sales\Model\Order\Payment $payment */
        $payment = $observer->getEvent()->getPayment();
        $instructionMethods = [
            Banktransfer::PAYMENT_METHOD_BANKTRANSFER_CODE,
            Cashondelivery::PAYMENT_METHOD_CASHONDELIVERY_CODE
        ];
        if (in_array($payment->getMethod(), $instructionMethods)) {
            $payment->setAdditionalInformation(
                'instructions',
                $payment->getMethodInstance()->getInstructions()
            );
        } elseif ($payment->getMethod() === Checkmo::PAYMENT_METHOD_CHECKMO_CODE) {
            $payment->setAdditionalInformation(
                'payable_to',
                $payment->getMethodInstance()->getPayableTo()
            );
            $payment->setAdditionalInformation(
                'mailing_address',
                $payment->getMethodInstance()->getMailingAddress()
            );
        }
    }
}