cforge-2.0.x-dev/modules/cforge_referrer/cforge_referrer.install

<?php
use Drupal\Core\Link;
use Drupal\Core\Url;

/**
 * Implements hook_install().
 */
function cforge_referrer_install() {
  \Drupal::config('cforge_referrer.settings');
  drupal::messenger()->addStatus(
    Link::fromTextAndUrl(
      t('Configure the referrer rewards'),
      Url::fromRoute('cforge.settings')
  ));
}

/**
 * Implements hook_uninstall().
 */
function cforge_referrer_uninstall() {
  \Drupal::service('user.data')->deleteAll('cforge_referrer', 'referred_by');
}