How can I use postsave method extending WebformHandlerBase for submitting to account fields
$account = \Drupal::currentUser();
    $user = \Drupal\user\Entity\User::load($account->id());
    $data = $webform_submission->getData();
    $photo = $data['picture'];
    $user->set('field_photo', $photo);
    $user->save();
  }
The above code, for example, will take a webform element, key is 'picture' and set it to an account field, 'field_photo'.