Including extension attributes when returning new group details

Author: JosephMaxwell

app/code/Magento/Customer/Model/ResourceModel/GroupRepository.php

@@ -156,6 +156,11 @@ public function save(\Magento\Customer\Api\Data\GroupInterface $group)
             ->setCode($groupModel->getCode())
             ->setTaxClassId($groupModel->getTaxClassId())
             ->setTaxClassName($groupModel->getTaxClassName());
+        
+        if ($group->getExtensionAttributes()) {
+            $groupDataObject->setExtensionAttributes($group->getExtensionAttributes());
+        }
+        
         return $groupDataObject;
     }