validateIBAN example

        $sErrorFlag = Shopware()->Container()->get('events')->filter('Sepa_Payment_Method_Validate_Data_Required', $sErrorFlag, [
            'subject' => $this,
            'paymentData' => $paymentData,
        ]);

        if (\count($sErrorFlag)) {
            $sErrorMessages[] = Shopware()->Snippets()->getNamespace('frontend/account/internalMessages')->get('ErrorFillIn', 'Please fill in all red fields');
        }

        if (isset($paymentData['sSepaIban']) && !$this->validateIBAN((string) $paymentData['sSepaIban'])) {
            $sErrorMessages[] = Shopware()->Snippets()->getNamespace('frontend/plugins/payment/sepa')->get('ErrorIBAN', 'Invalid IBAN');
            $sErrorFlag['sSepaIban'] = true;
        }

        if (\count($sErrorMessages)) {
            return [
                'sErrorFlag' => $sErrorFlag,
                'sErrorMessages' => $sErrorMessages,
            ];
        }