Add token exchange endpoint

src/API/TokenExchangeV3ToV5.php

@@ -0,0 +1,47 @@
+<?php
+/**
+ * Pinterest API Token exchnge class.
+ *
+ * @class       TokenExchangeV3ToV5
+ * @version     x.x.x
+ * @package     Pinterest_For_WordPress/Classes/
+ */
+
+namespace Automattic\WooCommerce\Pinterest\API;
+
+if ( ! defined( 'ABSPATH' ) ) {
+	exit;
+}
+
+/**
+ * V3 to V5 token exchange class.
+ * Contains the methods API methods and the update procedure.
+ *
+ * @since x.x.x
+ */
+class TokenExchangeV3ToV5 extends APIV5 {
+
+	const API_DOMAIN = 'https://api.pinterest.com/v3';
+
+	/**
+	 * Pull ads supported countries information from the API.
+	 *
+	 * @since x.x.x
+	 *
+	 * @return array $data {
+	 *     Contains token details.
+	 *
+	 *     @type string $access_token                   The access token for authentication.
+	 *     @type string $refresh_token                  The refresh token for acquiring a new access token.
+	 *     @type string $token_type                     Type of the token, usually "bearer".
+	 *     @type int    $expires_in                     Time in seconds when the access token expires.
+	 *     @type int    $refresh_token_expires_in       Time in seconds when the refresh token expires.
+	 *     @type string $scope                          The scope for which the access token has permission.
+	 * }
+	 */
+	public static function exchange_token() {
+		$request_url = 'oauth/commerce_integrations/token/exchange/';
+		return self::make_request( $request_url );
+	}
+
+}