Bulk Grant Feature #30
Description
Similar to #22 , it would be nice to be able to grant a permission in bulk.
For example, if a new feature is rolled out that many groups of actors should have enabled for them, it would be nice to say something like SomePermissionPolicy.grant_all!(companies, :a_permission).
Some potential challenges might be do we accept mixed types of actors like SomePermissionPolicy.grant_all!(groups_and_users, :a_permission) where it's a mix of Group and User actors? Or does this method accept only groups of actors of the same type for simplicity.