Merge pull request #5391 from magento-borg/MC-30925

Fixed Issues:
- MC-30925: Customer group API update

Author: dvoskoboinikov

app/code/Magento/Customer/etc/webapi.xml

@@ -141,6 +141,7 @@
         </resources>
         <data>
             <parameter name="customer.id" force="true">%customer_id%</parameter>
+            <parameter name="customer.group_id" force="true">null</parameter>
         </data>
     </route>
     <route url="/V1/customers/me" method="GET" soapOperation="getSelf">

dev/tests/api-functional/testsuite/Magento/Customer/Api/AccountManagementMeTest.php

@@ -16,6 +16,8 @@
 /**
  * Class AccountManagementMeTest
  *
+ * Tests involving the customer modifying their user information via web API.
+ *
  * @SuppressWarnings(PHPMD.CouplingBetweenObjects)
  * @magentoApiDataFixture Magento/Customer/_files/customer.php
  * @magentoApiDataFixture Magento/Customer/_files/customer_two_addresses.php
@@ -144,13 +146,14 @@ public function testUpdateCustomer()
     {
         $customerData = $this->_getCustomerData($this->customerData[CustomerInterface::ID]);
         $lastName = $customerData->getLastname();
-
+        $groupID = $customerData->getGroupId();
         $updatedCustomerData = $this->dataObjectProcessor->buildOutputDataArray(
             $customerData,
             \Magento\Customer\Api\Data\CustomerInterface::class
         );
         $updatedCustomerData[CustomerInterface::LASTNAME] = $lastName . 'Updated';
         $updatedCustomerData[CustomerInterface::ID] = 25;
+        $updatedCustomerData[CustomerInterface::GROUP_ID] = $groupID . 1;
 
         $serviceInfo = [
             'rest' => [
@@ -172,6 +175,7 @@ public function testUpdateCustomer()
 
         $customerData = $this->_getCustomerData($this->customerData[CustomerInterface::ID]);
         $this->assertEquals($lastName . "Updated", $customerData->getLastname());
+        $this->assertEquals($groupID, $customerData->getGroupId());
     }
 
     public function testGetCustomerData()