Add handling for billingCountry on update subscription

CRM/Core/Payment/MJWTrait.php

@@ -434,6 +434,10 @@ trait CRM_Core_Payment_MJWTrait {
       $propertyBag->setIsRecur(FALSE);
     }
 
+    if (!$propertyBag->has('billingCountry') && $propertyBag->has('country')) {
+      $propertyBag->setBillingCountry($propertyBag->getCustomProperty('country'));
+    }
+
     // Make sure we have a description for the contribution
     if (!$propertyBag->has('description')) {
       $propertyBag->setDescription(E::ts('Contribution: %1', [1 => $this->getPaymentProcessorLabel()]));
@@ -532,9 +536,12 @@ trait CRM_Core_Payment_MJWTrait {
       $propertyBag->setContributionRecurID($existingRecur['id']);
     }
 
-    // @fixme Billing properties don't really work properly without https://github.com/civicrm/civicrm-core/pull/21527
     // $propertyBag->setBillingCity($params['city'] ?? '');
-    // $propertyBag->setBillingCountry($params['country'] ?? '');
+    // @fixme Country: https://github.com/civicrm/civicrm-core/pull/28926 (5.71)
+    if (!$propertyBag->has('billingCountry') && $propertyBag->has('country')) {
+      $propertyBag->setBillingCountry($propertyBag->getCustomProperty('country'));
+    }
+    // $propertyBag->setBillingCountry($params['billingCountry'] ?? $params['country'] ?? '');
     // $propertyBag->setBillingStateProvince()
 
     $propertyBag->setCustomProperty('error_url', $this->getErrorUrl($propertyBag));