Assertions for Add/Attach/Detach Relations

[calvinps]

Is there a way to test if you can add/attach/detach relationships? Nova provides a way to authorize editing relationships on a resource: https://nova.laravel.com/docs/2.0/resources/authorization.html#relationships

If not, maybe this would make a good addition to the Policies assertions (e.g. assertCanAdd, assertCanAttach, assertCanDetach)?

[stevelacey]

Yeah this would be great, assertion of the pivot fields on add and edit attachment would also be handy

[dillingham]

PRs welcome