Extract simple workers common code into a base class [PREMIUM-4]

lib/Cron/Workers/KeyCheck/KeyCheckWorker.php

@@ -0,0 +1,38 @@
+<?php
+namespace MailPoet\Cron\Workers\KeyCheck;
+
+use MailPoet\Cron\CronHelper;
+use MailPoet\Cron\Workers\SimpleWorker;
+use MailPoet\Models\SendingQueue;
+use MailPoet\Services\Bridge;
+
+if(!defined('ABSPATH')) exit;
+
+abstract class KeyCheckWorker extends SimpleWorker {
+  const UNAVAILABLE_SERVICE_RESCHEDULE_TIMEOUT = 60;
+
+  public $bridge;
+
+  function initApi() {
+    if(!$this->bridge) {
+      $this->bridge = new Bridge();
+    }
+  }
+
+  function processQueueLogic(SendingQueue $queue) {
+    try {
+      $result = $this->checkKey();
+    } catch (\Exception $e) {
+      $result = false;
+    }
+
+    if(empty($result['code']) || $result['code'] == Bridge::CHECK_ERROR_UNAVAILABLE) {
+      $this->reschedule($queue, self::UNAVAILABLE_SERVICE_RESCHEDULE_TIMEOUT);
+      return false;
+    }
+
+    return true;
+  }
+
+  abstract function checkKey();
+}