Customize authentication manager and other services

WIP documentation page on how to override services, specifically the authentication manager.

composer require --dev friends-of-behat/service-container-extension

Put this in behat.yml:

    FriendsOfBehat\ServiceContainerExtension:
      imports:
        - "features/bootstrap/services.yml"

Then create the services.yml:

parameters:
  drupal.authentication_manager.class: FooAuthenticationManager

Create FooAuthenticationManager.php somewhere and extend from DrupalAuthenticationManager.

To have the class loaded, put it in composer.json autoload:

"autoload": {
        "classmap": [
            "features/bootstrap/FooAuthenticationManager.php"
        ]
    },
``