Querying polymorphic relations

[lindyhopchris]

At the moment querying polymorphic relationships is not well supported in 1.x. Need to review changes in this version of Laravel 5.8 and see whether we can improve polymorphs.
https://laravel-news.com/laravel-5-8-27

[lindyhopchris]

Closing in favour of this issue in the new package:
laravel-json-api/laravel#8