class UserData

class UserData extends DestinationBase implements ContainerFactoryPluginInterface {

  /**
   * @var \Drupal\user\UserData
   */
  protected $userData;

  /**
   * Builds a user data entity destination.
   *
   * @param array $configuration
   *   A configuration array containing information about the plugin instance.
   * @param string $plugin_id
   *   The plugin_id for the plugin instance.
   * @param mixed $plugin_definition
   *   The plugin implementation definition.
   * @param \Drupal\migrate\Plugin\MigrationInterface $migration
   *   The migration.
   * @param \Drupal\user\UserData $user_data
   *   The user data service.
   */
  public function __construct(array $configuration, $plugin_id, $plugin_definition, MigrationInterface $migration, UserDataStorage $user_data) {
    parent::__construct($configuration, $plugin_id, $plugin_definition, $migration);
    $this->userData = $user_data;
  }

  /**
   * {@inheritdoc}
   */
  public static function create(ContainerInterface $container, array $configuration, $plugin_id, $plugin_definition, MigrationInterface $migration = NULL) {
    return new static($configuration, $plugin_id, $plugin_definition, $migration, $container
      ->get('user.data'));
  }

  /**
   * {@inheritdoc}
   */
  public function import(Row $row, array $old_destination_id_values = []) {
    $uid = $row
      ->getDestinationProperty('uid');
    $module = $row
      ->getDestinationProperty('module');
    $key = $row
      ->getDestinationProperty('key');
    $this->userData
      ->set($module, $uid, $key, $row
      ->getDestinationProperty('settings'));
    return [
      $uid,
      $module,
      $key,
    ];
  }

  /**
   * {@inheritdoc}
   */
  public function getIds() {
    $ids['uid']['type'] = 'integer';
    $ids['module']['type'] = 'string';
    $ids['key']['type'] = 'string';
    return $ids;
  }

  /**
   * {@inheritdoc}
   */
  public function fields() {
    return [
      'uid' => 'The user id.',
      'module' => 'The module name responsible for the settings.',
      'key' => 'The setting key to save under.',
      'settings' => 'The settings to save.',
    ];
  }

}