Use route access not custom code

Problem/Motivation

I would like to add custom access check to routing entity.group.group_request_membership with RouteSubscriber.

  protected function alterRoutes(RouteCollection $collection) {
    if ($route = $collection->get('entity.group.group_request_membership')) {
      $route->setRequirement('_my_custom_access', 'FALSE');
    }
  }

The problem is when the modul rendering "Request group membership" or "Request membership" link then it has own logic in code. We must use $url->access($account) to render link when route is available.

When own logic needed it's ok to extend, but I suggest to also use $url->access($account) because if it's false then route is unavailable.

For example:

Old:

      if ($group->hasPermission('request group membership', $this->currentUser)) {
        $build = $group->toLink($this->t('Request Membership'), 'group-request-membership')
          ->toString();
      }

New:

      $link = $group->toLink($this->t('Request Membership'), 'group-request-membership');
      if($link->getUrl()->access($this->currentUser)){
        $build = $link->toString();
      }