refactor(notifications): standardize getRecipients method signatures

app/Notifications/Notification.php

@@ -0,0 +1,22 @@
+<?php
+
+namespace Illuminate\Notifications;
+
+use App\Notifications\Channels\SendsEmail;
+use App\Notifications\Dto\DiscordMessage;
+use App\Notifications\Dto\PushoverMessage;
+use App\Notifications\Dto\SlackMessage;
+use Illuminate\Notifications\Messages\MailMessage;
+
+interface Notification
+{
+    public function toMail(SendsEmail $notifiable): MailMessage;
+
+    public function toPushover(): PushoverMessage;
+
+    public function toDiscord(): DiscordMessage;
+
+    public function toSlack(): SlackMessage;
+
+    public function toTelegram();
+}