Replace deprecated SwiftMailer with Symfony Mailer

Some tests with BCC addresses needed to be changed because SwiftMailer
contained a bug with handling BCC addresses that Symfony Mailer does
not.

composer.json

@@ -33,12 +33,12 @@
         "phpmd/phpmd": "^2.9.1",
         "phpunit/phpunit": "^8.0",
         "php-http/curl-client": "^2.0",
-        "swiftmailer/swiftmailer": "6.2.3",
         "phpstan/phpstan": "^0.12.64",
         "pdepend/pdepend": "^2.5",
         "nyholm/psr7": "^1.2",
         "doctrine/coding-standard": "^8.0",
         "php-parallel-lint/php-parallel-lint": "^1.2",
-        "egulias/email-validator": "^2.1.23"
+        "egulias/email-validator": "^2.1.23",
+        "symfony/mailer": "^5.0"
     }
 }

tests/MessageTrait.php

@@ -2,15 +2,15 @@
 
 namespace rpkamp\Mailhog\Tests;
 
-use RuntimeException;
-use Swift_Mailer;
-use Swift_Message;
-use Swift_SmtpTransport;
+use Symfony\Component\Mailer\Mailer;
+use Symfony\Component\Mailer\MailerInterface;
+use Symfony\Component\Mailer\Transport;
+use Symfony\Component\Mime\Email;
 
 trait MessageTrait
 {
     /**
-     * @var Swift_Mailer
+     * @var MailerInterface
      */
     private $mailer;
 
@@ -21,29 +21,29 @@ public function sendDummyMessage(): void
         );
     }
 
-    public function createDummyMessage(): Swift_Message
+    public function createDummyMessage(): Email
     {
         return $this->createBasicMessage('me@myself.example', 'myself@myself.example', 'Hello', 'How are you?');
     }
 
-    public function createBasicMessage(string $from, string $to, string $subject, string $body): Swift_Message
+    public function createBasicMessage(string $from, string $to, string $subject, string $body): Email
     {
-        return (new Swift_Message())
-            ->setFrom($from)
-            ->setTo($to)
-            ->setSubject($subject)
-            ->setBody($body);
+        return (new Email())
+            ->from($from)
+            ->to($to)
+            ->subject($subject)
+            ->text($body);
     }
 
-    public function sendMessage(Swift_Message $message): void
+    public function sendMessage(Email $message): void
     {
         $this->getMailer()->send($message);
     }
 
-    private function getMailer(): Swift_Mailer
+    private function getMailer(): MailerInterface
     {
         if (null === $this->mailer) {
-            $this->mailer = new Swift_Mailer(new Swift_SmtpTransport(MailhogConfig::getHost(), MailhogConfig::getPort()));
+            $this->mailer = new Mailer(Transport::fromDsn($_ENV['mailhog_smtp_dsn']));
         }
 
         return $this->mailer;