Move cron-scheduling logic from SimpleWorker to CronWorkerRunner

[MAILPOET-2539]

lib/Cron/CronWorkerInterface.php

@@ -0,0 +1,38 @@
+<?php
+
+namespace MailPoet\Cron;
+
+use MailPoet\Models\ScheduledTask;
+
+interface CronWorkerInterface {
+  /** @return string */
+  function getTaskType();
+
+  /** @return bool */
+  function scheduleAutomatically();
+
+  /** @return bool */
+  function supportsMultipleInstances();
+
+  /** @return bool */
+  function checkProcessingRequirements();
+
+  function init();
+
+  /**
+   * @param ScheduledTask $task
+   * @param float $timer
+   * @return bool
+   */
+  function prepareTaskStrategy(ScheduledTask $task, $timer);
+
+  /**
+   * @param ScheduledTask $task
+   * @param float $timer
+   * @return bool
+   */
+  function processTaskStrategy(ScheduledTask $task, $timer);
+
+  /** @return \DateTimeInterface */
+  function getNextRunDate();
+}