feat: add invite notification emails, functionality to admin dashboard and sign up page

Signed-off-by: Miguel Nogueira <me@nogueira.codes>

app/Mail/InvitedToApp.php

@@ -0,0 +1,57 @@
+<?php
+
+namespace App\Mail;
+
+use App\Invitation;
+use Illuminate\Bus\Queueable;
+use Illuminate\Contracts\Queue\ShouldQueue;
+use Illuminate\Mail\Mailable;
+use Illuminate\Mail\Mailables\Content;
+use Illuminate\Mail\Mailables\Envelope;
+use Illuminate\Queue\SerializesModels;
+
+class InvitedToApp extends Mailable implements ShouldQueue
+{
+    use Queueable, SerializesModels;
+
+    /**
+     * Create a new message instance.
+     */
+    public function __construct(public Invitation $invitation)
+    {
+        //
+    }
+
+    /**
+     * Get the message envelope.
+     */
+    public function envelope(): Envelope
+    {
+        return new Envelope(
+            subject: 'You\'ve just been invited to ' . config('app.name'),
+        );
+    }
+
+    /**
+     * Get the message content definition.
+     */
+    public function content(): Content
+    {
+        return new Content(
+            view: 'mail.invited-to-app',
+            with: [
+                'token' => $this->invitation->invitation_code
+            ]
+        );
+    }
+
+    /**
+     * Get the attachments for the message.
+     *
+     * @return array<int, \Illuminate\Mail\Mailables\Attachment>
+     */
+    public function attachments(): array
+    {
+        return [];
+    }
+}