Added email gateway migration (#328)

src/Migration/EmailGatewayMigration.php

@@ -0,0 +1,28 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Terminal42\NotificationCenterBundle\Migration;
+
+use Contao\CoreBundle\Migration\AbstractMigration;
+use Contao\CoreBundle\Migration\MigrationResult;
+use Doctrine\DBAL\Connection;
+
+class EmailGatewayMigration extends AbstractMigration
+{
+    public function __construct(private readonly Connection $connection)
+    {
+    }
+
+    public function shouldRun(): bool
+    {
+        return $this->connection->fetchOne("SELECT COUNT(*) FROM tl_nc_gateway WHERE type='email'") > 0;
+    }
+
+    public function run(): MigrationResult
+    {
+        $this->connection->executeStatement("UPDATE tl_nc_gateway SET type='mailer' WHERE type='email'");
+
+        return $this->createResult(true);
+    }
+}