Implement advanced authorization checks using roles and policies

[danharrin]

This PR adds support for advanced authorization control in Filament.

Filament provides three levels of authorization. Each is checked, in this order. If one level is not present, it is ignored:

• Filament admin users will have complete control over all data available in your Filament panel.
• Roles allow basic control over access to pages, resources and the actions that take place within them.
• Model policies extend the same feature set as roles, as well as providing record-specific control over user access to certain actions.

Example advanced authorization using roles

public static function authorization()
{
    return [
        Roles\Guest::allow()->only('viewAny'),
        Roles\Employee::allow()->except('delete'),
        Roles\Manager::allow(),
    ];
}

[kfvit-andreaskviby]

Hey, just a thought from Mr Kviby here :) I would like to add if the record is viewable at all for the currently logged in user.

[ryangjchandler]

Hey, just a thought from Mr Kviby here :) I would like to add if the record is viewable at all for the currently logged in user.

You would be able to do this using a model policy or using one of Filament's roles.