Adding charged currency hidden config field (#935)

Model/Config/Source/ChargedCurrency.php

+<?php
+/**
+ *                       ######
+ *                       ######
+ * ############    ####( ######  #####. ######  ############   ############
+ * #############  #####( ######  #####. ######  #############  #############
+ *        ######  #####( ######  #####. ######  #####  ######  #####  ######
+ * ###### ######  #####( ######  #####. ######  #####  #####   #####  ######
+ * ###### ######  #####( ######  #####. ######  #####          #####  ######
+ * #############  #############  #############  #############  #####  ######
+ *  ############   ############  #############   ############  #####  ######
+ *                                      ######
+ *                               #############
+ *                               ############
+ *
+ * Adyen Payment module (https://www.adyen.com/)
+ *
+ * Copyright (c) 2020 Adyen BV (https://www.adyen.com/)
+ * See LICENSE.txt for license details.
+ *
+ * Author: Adyen <magento@adyen.com>
+ */
+
+namespace Adyen\Payment\Model\Config\Source;
+
+use Magento\Framework\Data\OptionSourceInterface;
+
+class ChargedCurrency implements OptionSourceInterface
+{
+    public function toOptionArray()
+    {
+        return array(
+            ['value' => 'display', 'label' => 'Display currency'],
+            ['value' => 'base', 'label' => 'Global/Website currency']
+        );
+    }
+}

etc/adminhtml/system/adyen_required_settings.xml

@@ -69,7 +69,12 @@
             <comment><![CDATA[Provide the unique live url prefix: <strong>[random]-[company name]</strong> from the "API URLs and Response" menu in the Adyen Customer Area. For more information, please check <a href="https://docs.adyen.com/developers/development-resources/live-endpoints#checkoutendpoints">  our documentation</a>.]]></comment>
             <config_path>payment/adyen_abstract/live_endpoint_url_prefix</config_path>
         </field>
-
+        <field id="charged_currency" translate="label" type="hidden" sortOrder="80" showInDefault="1" showInWebsite="1" showInStore="1">
+            <label>Charged currency</label>
+            <comment><![CDATA[Currency used for Adyen payment processing. This setting is hidden to ensure processing of payments in the expected currency (Display by default), see <a target="_blank" href="https://docs.adyen.com/developers/plugins/magento-2/set-up-the-plugin-in-magento#selecting-charged-currency">Adyen docs</a> for more information.]]></comment>
+            <source_model>Adyen\Payment\Model\Config\Source\ChargedCurrency</source_model>
+            <config_path>payment/adyen_abstract/charged_currency</config_path>
+        </field>
         <field id="capture_mode" translate="label" type="select" sortOrder="90" showInDefault="1" showInWebsite="1" showInStore="1">
             <label>Capture Delay</label>
             <tooltip>Immediate is the default. Set to manual if you want to perform the capture of funds manually later (only affects credit cards and a few alternative payment methods). You need to change this setting as well in Adyen Customer Area => Settings => Merchant Settings => Capture Delay. If you have selected a capture delay of a couple of days in Adyen keep it here on immediate</tooltip>