Inheritance: implements AuthBucket\OAuth2\Model\ModelInterface, implements Symfony\Component\Security\Core\User\UserInterface
 public function load(ObjectManager $manager)
 {
     $model = new User();
     $model->setUsername('demousername1')->setPassword('demopassword1')->setRoles(['ROLE_USER']);
     $manager->persist($model);
     $model = new User();
     $model->setUsername('demousername2')->setPassword('demopassword2')->setRoles(['ROLE_USER']);
     $manager->persist($model);
     $model = new User();
     $model->setUsername('demousername3')->setPassword('demopassword3')->setRoles(['ROLE_USER']);
     $manager->persist($model);
     $manager->flush();
 }