Call to undefined method MagentoSalesApiDataOrderItemExtension

Error: Call to undefined method MagentoSalesApiDataOrderItemExtension::setGuid()

di.xml

<?xml version="1.0"?>
<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:framework:ObjectManager/etc/config.xsd">
     <type name="MagentoSalesApiOrderItemRepositoryInterface">
        <plugin name="guid_extension_attribute" type="ConvertGUIDPluginOrderItemRepositoryPlugin" />
     </type>
</config>

extension_attributes.xml

<?xml version="1.0"?>
<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:framework:Api/etc/extension_attributes.xsd">
    <extension_attributes for="MagentoSalesApiDataOrderInterface">
        <attribute code="guid" type="string"/>
    </extension_attributes>
</config>

OrderItemRepositoryPlugin.php

<?php

namespace ConvertGUIDPlugin;

use MagentoSalesApiDataOrderItemExtensionFactory;
use MagentoSalesApiDataOrderItemExtensionInterface;
use MagentoSalesApiDataOrderItemInterface;
use MagentoSalesApiDataOrderItemSearchResultInterface;
use MagentoSalesApiOrderItemRepositoryInterface;

/**
 * Class OrderItemRepositoryPlugin
 */
class OrderItemRepositoryPlugin
{
    /**
     * Order feedback field name
     */
    const FIELD_NAME = 'guid';

    /**
     * Order Extension Attributes Factory
     *
     * @var OrderItemExtensionFactory
     */
    protected $extensionFactory;

    /**
     * OrderItemRepositoryPlugin constructor
     *
     * @param OrderItemExtensionFactory $extensionFactory
     */
    public function __construct(OrderItemExtensionFactory $extensionFactory)
    {
        $this->extensionFactory = $extensionFactory;
    }

    /**
     *
     * @param OrderItemRepositoryInterface $subject
     * @param OrderItemInterface $orderItem
     *
     * @return OrderItemInterface
     */
    public function afterGet(OrderItemRepositoryInterface $subject, OrderItemInterface $orderItem)
    {
        $guid = $orderItem->getData(self::FIELD_NAME);
        $extensionAttributes = $orderItem->getExtensionAttributes();
        $extensionAttributes = $extensionAttributes ? $extensionAttributes : $this->extensionFactory->create();
        $extensionAttributes->setGuid($guid);
        $orderItem->setExtensionAttributes($extensionAttributes);

        return $orderItem;
    }

    /**
     *
     * @param OrderItemRepositoryInterface $subject
     * @param OrderItemSearchResultInterface $searchResult
     *
     * @return OrderItemSearchResultInterface
     */
    public function afterGetList(OrderItemRepositoryInterface $subject, OrderItemSearchResultInterface $searchResult)
    {
        $orderItems = $searchResult->getItems();

        foreach ($orderItems as &$item) {
            $guid = $item->getData(self::FIELD_NAME);
            $extensionAttributes = $item->getExtensionAttributes();
            $extensionAttributes = $extensionAttributes ? $extensionAttributes : $this->extensionFactory->create();
            $extensionAttributes->setGuid($guid);
            $item->setExtensionAttributes($extensionAttributes);
        }

        return $searchResult;
    }
}