code: public function boot(Factory $validator)
      {
          $passwordStrength = app('passwordStrength');
          $translator = app('passwordStrength.translationProvider')->get($validator);
  
          foreach(['letters', 'numbers', 'caseDiff', 'symbols'] as $rule) {
              $snakeCasedRule = snake_case($rule);
  
              $validator->extend($rule, function ($_, $value, $__) use ($passwordStrength, $rule) {
                  $capitalizedRule = ucfirst($rule);
                  return call_user_func([$passwordStrength, "validate{$capitalizedRule}"], $value);
              }, $translator->get("password-strength::validation.{$snakeCasedRule}"));
          }
      }
docs: Bootstrap application services.
  
  @return void