Add birthdate check on the pay for order page for in3 payment method

src/Gateway/GatewayModule.php

@@ -6,6 +6,7 @@
 
 namespace Mollie\WooCommerce\Gateway;
 
+use Automattic\WooCommerce\Admin\Overrides\Order;
 use Automattic\WooCommerce\Internal\DataStores\Orders\CustomOrdersTableController;
 use Mollie\WooCommerce\Vendor\Inpsyde\Modularity\Module\ExecutableModule;
 use Mollie\WooCommerce\Vendor\Inpsyde\Modularity\Module\ModuleClassNameIdTrait;
@@ -58,6 +59,8 @@ class GatewayModule implements ServiceModule, ExecutableModule
      */
     protected $pluginId;
 
+    const FIELD_IN3_BIRTHDATE = 'billing_birthdate';
+
     public function services(): array
     {
         return [
@@ -255,6 +258,11 @@ static function () {
                 11,
                 2
             );
+            add_action(
+                'woocommerce_before_pay_action',
+                [$this, 'in3FieldsMandatoryPayForOrder'],
+                11
+            );
         }
         // Set order to paid and processed when eventually completed without Mollie
         add_action('woocommerce_payment_complete', [$this, 'setOrderPaidByOtherGateway'], 10, 1);
@@ -622,12 +630,32 @@ public function in3FieldsMandatory($fields, $errors)
     {
         $gatewayName = "mollie_wc_gateway_in3";
         $phoneField = 'billing_phone';
-        $birthdateField = 'billing_birthdate';
+        $birthdateField = self::FIELD_IN3_BIRTHDATE;
         $paymentMethodName = 'in3';
         $fields = $this->addPaymentMethodMandatoryFields($fields, $gatewayName, $phoneField, $errors, $paymentMethodName);
         return $this->addPaymentMethodMandatoryFields($fields, $gatewayName, $birthdateField, $errors, $paymentMethodName);
     }
 
+    /**
+     * @param Order $order
+     */
+    public function in3FieldsMandatoryPayForOrder(Order $order)
+    {
+        $birthdateValue = filter_input(INPUT_POST, self::FIELD_IN3_BIRTHDATE, FILTER_SANITIZE_SPECIAL_CHARS) ?? false;
+        if (!$birthdateValue) {
+            wc_add_notice(
+                sprintf(
+                    __(
+                        'Error processing %1$s payment, the birthdate field is required.',
+                        'mollie-payments-for-woocommerce'
+                    ),
+                    $order->get_payment_method_title()
+                ),
+                'error'
+            );
+        }
+    }
+
     /**
      * @param string $id
      * @param IconFactory $iconFactory