Use DBAL Driver middleware to handle the correct connection timezone

I looked into using DBAL events for this but found that DBAL events
are deprecated so I went with middleware as they are recommended
as a replacement for the DBAL events.
[MAILPOET-6142]

mailpoet/lib/Doctrine/Middlewares/PostConnectMiddleware.php

@@ -0,0 +1,14 @@
+<?php declare(strict_types = 1);
+
+namespace MailPoet\Doctrine\Middlewares;
+
+use MailPoetVendor\Doctrine\DBAL\Driver\Connection;
+use MailPoetVendor\Doctrine\DBAL\Driver\Middleware\AbstractDriverMiddleware;
+
+class PostConnectMiddleware extends AbstractDriverMiddleware {
+  public function connect(array $params): Connection {
+    $connection = parent::connect($params);
+    $connection->exec('SET time_zone = "+00:00"');
+    return $connection;
+  }
+}