entity_legal-4.0.x-dev/tests/modules/entity_legal_test/entity_legal_test.module

<?php

/**
 * @file
 * Contains entity_legal_test.module.
 */

use Drupal\user\UserInterface;

/**
 * Implements hook_user_login().
 */
function entity_legal_test_user_login(UserInterface $account) {
  \Drupal::messenger()
    ->addStatus('A status message sample')
    ->addWarning('A warning message sample')
    ->addError('An error message sample');
}