Run the polymorphic bug

[bf4]

Making a PR with just the failing test from https://github.com/cerebris/jsonapi-resources/issues/1305

I see

No class name found for #<Class:#<ContactMedium:0x00007f93d23acb00>> (Responds to ActiveModel::Naming but Class name cannot be blank. You need to supply a name argument when anonymous class given)
No class name found for #<Class:#<Individual:0x00007f93d23bd6f8>> (Responds to ActiveModel::Naming but Class name cannot be blank. You need to supply a name argument when anonymous class given)
No class name found for #<Class:#<ContactMedium:0x00007f93d641cb90>> (Responds to ActiveModel::Naming but Class name cannot be blank. You need to supply a name argument when anonymous class given)
No class name found for #<Class:#<Individual:0x00007f93d6424408>> (Responds to ActiveModel::Naming but Class name cannot be blank. You need to supply a name argument when anonymous class given)
No class name found for #<Class:#<ContactMedium:0x00007f93d684d7a0>> (Responds to ActiveModel::Naming but Class name cannot be blank. You need to supply a name argument when anonymous class given)
No class name found for #<Class:#<Individual:0x00007f93d646f9d0>> (Responds to ActiveModel::Naming but Class name cannot be blank. You need to supply a name argument when anonymous class given)