feat/Visibility

[JohanHjelsethStorstad]

A system that is an alternative to permissions. The system is much more dynamic than permissions. A thing using visibility will be authored on the instance level (row in db) instead of at the table level. The auth is based on which groups a user is member of.

It includes levels for different levels of authorization. And a system to have 'special' visibility that links visibility to a permission rather than a set of groups. The system will be used for all cms including news, images (collections), and events.