refactor: replace custom CRM with Monica fork

app/Interfaces/MailNotification.php

@@ -0,0 +1,17 @@
+<?php
+
+namespace App\Interfaces;
+
+use App\Models\User\User;
+use Illuminate\Notifications\Messages\MailMessage;
+
+interface MailNotification
+{
+    /**
+     * Get the mail representation of the notification.
+     *
+     * @param  User  $user
+     * @return \Illuminate\Notifications\Messages\MailMessage
+     */
+    public function toMail(User $user): MailMessage;
+}