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

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

app/Invitation.php

@@ -0,0 +1,18 @@
+<?php
+
+namespace App;
+
+use App\Policies\InvitationPolicy;
+use Illuminate\Database\Eloquent\Attributes\UsePolicy;
+use Illuminate\Database\Eloquent\Model;
+
+#[UsePolicy(InvitationPolicy::class)]
+class Invitation extends Model
+{
+    protected function casts(): array
+    {
+        return [
+            'expiration' => 'datetime'
+        ];
+    }
+}