Add Mattermost notifier bridge

Author: thePanz

CHANGELOG.md

@@ -4,6 +4,7 @@ CHANGELOG
 5.1.0
 -----
 
+ * Added the Mattermost notifier bridge
 * [BC BREAK] The `ChatMessage::fromNotification()` method's `$recipient` and `$transport`
   arguments were removed.
 * [BC BREAK] The `EmailMessage::fromNotification()` and `SmsMessage::fromNotification()`

Exception/UnsupportedSchemeException.php

@@ -30,6 +30,10 @@ class UnsupportedSchemeException extends LogicException
             'class' => Bridge\Telegram\TelegramTransportFactory::class,
             'package' => 'symfony/telegram-notifier',
         ],
+        'mattermost' => [
+            'class' => Bridge\Mattermost\MattermostTransportFactory::class,
+            'package' => 'symfony/mattermost-notifier',
+        ],
         'nexmo' => [
             'class' => Bridge\Nexmo\NexmoTransportFactory::class,
             'package' => 'symfony/nexmo-notifier',

Transport.php

@@ -11,6 +11,7 @@
 
 namespace Symfony\Component\Notifier;
 
+use Symfony\Component\Notifier\Bridge\Mattermost\MattermostTransportFactory;
 use Symfony\Component\Notifier\Bridge\Nexmo\NexmoTransportFactory;
 use Symfony\Component\Notifier\Bridge\Slack\SlackTransportFactory;
 use Symfony\Component\Notifier\Bridge\Telegram\TelegramTransportFactory;
@@ -36,6 +37,7 @@ class Transport
     private const FACTORY_CLASSES = [
         SlackTransportFactory::class,
         TelegramTransportFactory::class,
+        MattermostTransportFactory::class,
         NexmoTransportFactory::class,
         TwilioTransportFactory::class,
     ];