magento-test/app/code/Magento/DirectoryGraphQl/etc/graphql/di.xml

<?xml version="1.0"?>
<!--
/**
 * Copyright © Magento, Inc. All rights reserved.
 * See COPYING.txt for license details.
 */
-->
<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:framework:ObjectManager/etc/config.xsd">
    <type name="Magento\GraphQl\Controller\HttpRequestProcessor">
        <arguments>
            <argument name="graphQlHeaders" xsi:type="array">
                <item name="Content-Currency" xsi:type="object">Magento\DirectoryGraphQl\Controller\HttpHeaderProcessor\CurrencyProcessor</item>
            </argument>
            <argument name="requestValidators" xsi:type="array">
                <item name="currencyValidator" xsi:type="object">Magento\DirectoryGraphQl\Controller\HttpRequestValidator\CurrencyValidator</item>
            </argument>
        </arguments>
    </type>
    <type name="Magento\DirectoryGraphQl\Controller\HttpHeaderProcessor\CurrencyProcessor">
        <arguments>
            <argument name="session" xsi:type="object">Magento\Framework\Session\Generic\Proxy</argument>
        </arguments>
    </type>
</config>