extracted interfaces for services, to aid in creating tests

src/Service/BackupCodeInterface.php

@@ -0,0 +1,26 @@
+<?php
+
+namespace App\Service;
+
+
+use Exception;
+use Psr\Cache\InvalidArgumentException;
+
+/** backup-codes are case‑insensitive alphanumeric strings
+ * they are single-use and marked as used after successful authentication */
+interface BackupCodeInterface {
+    /** generate a set of backup-codes and return them
+     * @param int $count Number of codes to generate
+     * @return string[] Generated backup codes
+     * @throws InvalidArgumentException|Exception */
+    public function generate(int $count = 0): array;
+
+    /** @throws InvalidArgumentException */
+    public function expire(): void;
+
+    /** check if backup-code is valid and mark it as used
+     * @param string $code Code supplied by the client
+     * @return bool true if the code is valid and unused
+     * @throws InvalidArgumentException */
+    public function verifyAndConsume(string $code): bool;
+}