Pass custom data to assert function

[epaezrubio]

It would be a nice touch if I was able to use a fourth argument in the assertion function to verify against single instances or other arbitrary custom data. Example, considering the current identity name to be Dezmond:

var ownPost = { 
    owner: "Dezmond"
}

var post = { 
    owner: "Foo"
}

AclService.allow('Manager', 'Post');
AclService.allow('User', 'Post', null, function (role, resource, privilege, data) {
    return role.name === data.owner;
});

AclService.can('Manager', 'Post', null, post) // true
AclService.can('User', 'Post', null, ownPost) // true
AclService.can('User', 'Post', null, post) // false
AclService.can('User', 'Post', null) // true

This would add way more flexibility to how one can use the can or isAllowed functions and, if I'm not wrong, it doesn't break any current interface.

I'd be happy to submit a PR implementing this feature.

Best.

[StyleT]

Hi!
I think you can pass an object as a first parameter and use data from it in the assertion.
The only thing that object should follow AclResourceInterface.

https://github.com/StyleT/js-acl/blob/master/src/index.js#L91