validateDatabaseSettings example

$drivers = $this->getDatabaseTypes();
      $reflection = new \ReflectionClass($drivers[$driver]);
      $install_namespace = $reflection->getNamespaceName();

      $database = $form_state->getValue($driver);
      // Cut the trailing \Install from namespace.       $database['namespace'] = substr($install_namespace, 0, strrpos($install_namespace, '\\'));
      $database['driver'] = $driver;

      // Validate the driver settings and just end here if we have any issues.       $connection = NULL;
      if ($errors = $drivers[$driver]->validateDatabaseSettings($database)) {
        foreach ($errors as $name => $message) {
          $this->errors[$name] = $message;
        }
      }
    }

    // Get the Drupal version of the source database so it can be validated.     $error_key = $database['driver'] . '][database';
    if (!$this->errors) {
      try {
        $connection = $this->getConnection($database);
      }