Add Laravel 13 compatibility and Slack webhook signature fix

Author: Copilot

.github/workflows/tests.yml

@@ -12,12 +12,16 @@ jobs:
       fail-fast: true
       matrix:
         php: [8.1, 8.2, 8.3]
-        laravel: ['10.*', '11.*', '12.*']
+        laravel: ['10.*', '11.*', '12.*', '13.*']
         exclude:
           - laravel: 11.*
             php: 8.1
           - laravel: 12.*
             php: 8.1
+          - laravel: 13.*
+            php: 8.1
+          - laravel: 13.*
+            php: 8.2
 
     name: P${{ matrix.php }} - L${{ matrix.laravel }}
 

src/Channels/DiscordWebhookChannel.php

@@ -8,6 +8,7 @@
 use GuzzleHttp\Client as HttpClient;
 use Illuminate\Notifications\Channels\SlackWebhookChannel;
 use Illuminate\Notifications\Messages\SlackMessage;
+use Illuminate\Notifications\Slack\SlackMessage as LaravelSlackMessage;
 use Illuminate\Notifications\Notification;
 
 class DiscordWebhookChannel
@@ -46,7 +47,7 @@ public function send($notifiable, Notification $notification)
 
         $message = $notification->toDiscord($notifiable);
 
-        if($message instanceof SlackMessage) {
+        if ($message instanceof SlackMessage || $message instanceof LaravelSlackMessage) {
             $slackWebhook = new SlackWebhookChannel($this->http);
             return $this->http->post($url . '/slack', $slackWebhook->buildJsonPayload($message));
         }