Send error if email is already used

app/Http/Controllers/UserController.php

@@ -31,7 +31,7 @@ class UserController extends Controller
 
         $request->validate([
             'phone' => ['required', 'phone:FR,national'],
-            'email' => 'required|email:strict,rfc',
+            'email' => ['required', 'email:strict,rfc', 'unique:users,email'],
         ]);
 
         $phone = new PhoneNumber($request["phone"], 'FR');