Session settings and $cookie_domain global moved to container parameters

Session ini settings and the $cookie_domain global variable were moved to container parameters. In addition request-dependent session ini settings (like, e.g. session.cookie_secure) are now populated by the session_configuration service instead of being hard-coded in DrupalKernel. Contrib modules which need to customize session settings now may do so by replacing that service.

Existing sites should copy session.storage.options from default.services.yml into their services.yml. If session related ini settings were customized in settings.php, they should be replicated in services.yml. Finally all session related settings including $cookie_domain should be removed from settings.php.