ENGCOM-7618: Update Customer data with REST API #28332

 - Merge Pull Request #28332 from engcom-Charlie/magento2:21237
 - Merged commits:
   1. 4afc05f
   2. d6d15d7
   3. cdbf988
   4. fe62842

Author: magento-engcom-team

app/code/Magento/Customer/Model/Plugin/UpdateCustomer.php

@@ -0,0 +1,81 @@
+<?php
+/**
+ * Copyright © Magento, Inc. All rights reserved.
+ * See COPYING.txt for license details.
+ */
+
+declare(strict_types=1);
+
+namespace Magento\Customer\Model\Plugin;
+
+use Magento\Framework\Webapi\Rest\Request as RestRequest;
+use Magento\Customer\Api\Data\CustomerInterface;
+use Magento\Customer\Api\CustomerRepositoryInterface;
+
+/**
+ * Update customer by id from request param
+ */
+class UpdateCustomer
+{
+    /**
+     * @var RestRequest
+     */
+    private $request;
+
+    /**
+     * @param RestRequest $request
+     */
+    public function __construct(RestRequest $request)
+    {
+        $this->request = $request;
+    }
+
+    /**
+     * Update customer by id from request if exist
+     *
+     * @param CustomerRepositoryInterface $customerRepository
+     * @param CustomerInterface $customer
+     * @param string|null $passwordHash
+     * @return array
+     */
+    public function beforeSave(
+        CustomerRepositoryInterface $customerRepository,
+        CustomerInterface $customer,
+        ?string $passwordHash = null
+    ): array {
+        $customerId = $this->request->getParam('customerId');
+
+        if ($customerId) {
+            $customer = $this->getUpdatedCustomer($customerRepository->getById($customerId), $customer);
+        }
+
+        return [$customer, $passwordHash];
+    }
+
+    /**
+     * Return updated customer
+     *
+     * @param CustomerInterface $originCustomer
+     * @param CustomerInterface $customer
+     * @return CustomerInterface
+     */
+    private function getUpdatedCustomer(
+        CustomerInterface $originCustomer,
+        CustomerInterface $customer
+    ): CustomerInterface {
+        $newCustomer = clone $originCustomer;
+        foreach ($customer->__toArray() as $name => $value) {
+            if ($name === CustomerInterface::CUSTOM_ATTRIBUTES) {
+                $value = $customer->getCustomAttributes();
+            } elseif ($name === CustomerInterface::EXTENSION_ATTRIBUTES_KEY) {
+                $value = $customer->getExtensionAttributes();
+            } elseif ($name === CustomerInterface::KEY_ADDRESSES) {
+                $value = $customer->getAddresses();
+            }
+
+            $newCustomer->setData($name, $value);
+        }
+
+        return $newCustomer;
+    }
+}

app/code/Magento/Customer/etc/webapi_rest/di.xml

@@ -19,4 +19,7 @@
             </argument>
         </arguments>
     </type>
+    <type name="Magento\Customer\Api\CustomerRepositoryInterface">
+        <plugin name="updateCustomerByIdFromRequest" type="Magento\Customer\Model\Plugin\UpdateCustomer" />
+    </type>
 </config>