make Message classes extensible

Author: bitgandtter

Message/ChatMessage.php

@@ -16,7 +16,7 @@
 /**
  * @author Fabien Potencier <fabien@symfony.com>
  */
-final class ChatMessage implements MessageInterface
+class ChatMessage implements MessageInterface
 {
     private ?string $transport = null;
     private string $subject;

Message/EmailMessage.php

@@ -23,7 +23,7 @@
 /**
  * @author Fabien Potencier <fabien@symfony.com>
  */
-final class EmailMessage implements MessageInterface
+class EmailMessage implements MessageInterface
 {
     private RawMessage $message;
     private ?Envelope $envelope;

Message/PushMessage.php

@@ -16,7 +16,7 @@
 /**
  * @author Tomas Norkūnas <norkunas.tom@gmail.com>
  */
-final class PushMessage implements MessageInterface
+class PushMessage implements MessageInterface
 {
     private $transport;
     private $subject;

Message/SmsMessage.php

@@ -18,7 +18,7 @@
 /**
  * @author Fabien Potencier <fabien@symfony.com>
  */
-final class SmsMessage implements MessageInterface
+class SmsMessage implements MessageInterface
 {
     private ?string $transport = null;
     private string $subject;