The default read-only implementation of PackageArticle.
The default read-only implementation of PackageArticle. You typically should not need to directly reference this class; instead, use the PackageArticle.apply method to construct new instances.
This Proxy trait allows you to extend the PackageArticle trait with additional state or behavior and implement the read-only methods from PackageArticle using an underlying instance.
Field information in declaration order.
Checks that all required fields are non-null.