When working with the RESTful Web Services module endpoints, the supported_auth values reference services tagged with authentication_provider. Out of the box, Drupal supports cookie authentication. The following code is provided by the basic_auth module to support the HTTP header authentication:

services:
  basic_auth.authentication.basic_auth:
    class: Drupal\basic_auth\Authentication\Provider\BasicAuth
    arguments: ['@config.factory', '@user.auth', '@flood', '@entity.manager']
    tags:
      - { name: authentication_provider, provider_id: 'basic_auth', priority: 100 }

An authentication provider can be created by creating a class in your module's Authentication\Provider namespace and implementing the \Drupal\Core\Authentication\AuthenticationProviderInterface interface. Then, register the class as a service in your module's services.yml.