Block actual preview route access

Good callout! I went a different route with the implementation, however. Instead of overriding the existing access_check.node.preview service the module provides it's own access_check.node.preview_permissions service. Drupal registers every access check provider using the applies_to property. If either the access_check.node.preview or access_check.node.preview_permissions access checker returns forbidden the preview route responds with access denied. Furthermore, the new service is used to set the preview button element access.

Automatically closed - issue fixed for 2 weeks with no activity.