InvitationRedemptionController.php

<?php

namespace Foo\Bar\Baz;

/**
 * url_handlers/routing would be required for this, could do a page class to reduce that portion of the code
 */
class InvitationRedemptionController extends Controller
{  
 public function index($request){
   if(!$this->requestHasParams($request)){
     //handle case where proper params aren't present
   }
   
   if($this->loginOrUpdateMember($request)){//method to handle login or update logic
     $this->redirect($request->getVar('YourProductURL'));
   }else{
     //return error message
   }
 }
  
  //additional supporting methods (requestHasParams(), loginOrUpdateMember(), any other methods you'd need to write)
}