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

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

app/Policies/InvitationPolicy.php

@@ -0,0 +1,37 @@
+<?php
+
+namespace App\Policies;
+
+use App\Invitation;
+use App\User;
+use Illuminate\Auth\Access\HandlesAuthorization;
+use Illuminate\Auth\Access\Response;
+
+class InvitationPolicy
+{
+    use HandlesAuthorization;
+
+    public function viewAny(User $user): bool
+    {
+
+    }
+
+    public function view(User $user, Invitation $invitation): Response
+    {
+        return $user->can('admin.manageInvitations') ? Response::allow() : Response::deny(__('You do not have permission to view invitations.'));
+    }
+
+    public function create(?User $user): Response
+    {
+        if (is_null($user)) {
+            return Response::allow();
+        }
+
+        return $user->can('admin.manageInvitations') ? Response::allow() : Response::deny(__('You do not have permission to request invitations.'));
+    }
+
+    public function delete(User $user, Invitation $invitation): Response
+    {
+        return $user->can('admin.manageInvitations') ? Response::allow() : Response::deny(__('You do not have permission to revoke invitations.'));
+    }
+}