Issue #2052389 by pwolanin: Fixed All elements added to the Request attributes should have a _ prepended unless they come from the path.
Issue #2043781 by pwolanin: Fixed Drupal::request()->attributes->get('account') may conflict with an account object loaded from the path.
Issue #1890878 by corvus_ch, ygerasimov, berenddeboer, Crell, fubhy the cat, effulgentsia: Add modular authentication system, including Http Basic; deprecate global .