391 Notification refactorings (#441)

* Refactor notifications to allow easier plugins

* Notification refactoring

* Formatting

* Move news to NewsService; cleanup of events

* More refactoring; added send email out for news item and the template

* Formatting

* Formatting

app/Notifications/Messages/AdminUserRegistered.php

@@ -0,0 +1,38 @@
+<?php
+
+namespace App\Notifications\Messages;
+
+use App\Models\User;
+use App\Notifications\BaseNotification;
+use App\Notifications\Channels\MailChannel;
+
+class AdminUserRegistered extends BaseNotification
+{
+    use MailChannel;
+
+    private $user;
+
+    /**
+     * Create a new notification instance.
+     *
+     * @param \App\Models\User $user
+     */
+    public function __construct(User $user)
+    {
+        parent::__construct();
+
+        $this->user = $user;
+        $this->setMailable(
+            'A new user registered',
+            'notifications.mail.admin.user.registered',
+            ['user' => $user]
+        );
+    }
+
+    public function toArray($notifiable)
+    {
+        return [
+            'user_id' => $this->user->id,
+        ];
+    }
+}