Add serializable DB connection wrapper

[MAILPOET-2014]

lib/Doctrine/SerializableConnection.php

@@ -0,0 +1,31 @@
+<?php
+
+namespace MailPoet\Doctrine;
+
+use MailPoetVendor\Doctrine\Common\EventManager;
+use MailPoetVendor\Doctrine\DBAL\Configuration;
+use MailPoetVendor\Doctrine\DBAL\Connection;
+use MailPoetVendor\Doctrine\DBAL\Driver;
+
+class SerializableConnection extends Connection {
+  private $params;
+  private $driver;
+  private $config;
+  private $event_manager;
+
+  function __construct(array $params, Driver $driver, Configuration $config = null, EventManager $event_manager = null) {
+    $this->params = $params;
+    $this->driver = $driver;
+    $this->config = $config;
+    $this->event_manager = $event_manager;
+    parent::__construct($params, $driver, $config, $event_manager);
+  }
+
+  function __sleep() {
+    return ['params', 'driver', 'config', 'event_manager'];
+  }
+
+  function __wakeup() {
+    parent::__construct($this->params, $this->driver, $this->config, $this->event_manager);
+  }
+}