ResourceTestBase uses incorrect resource type throughout itself

In doing this fix, it broke on the include for uid.roles for the owner field.

This error is caused when it tries to find the public field name for commerce_product_variation_type.

      foreach ($field_names as $key => $public_field_name) {
        $resource_type = $this->container->get('jsonapi.resource_type.repository')->get($entity->getEntityTypeId(), $entity->bundle());
        $field_name = $resource_type->getInternalName($public_field_name);

By this time the entity has turned into the product and is no longer the variation.

Okay, so I was wrong about this and misunderstood how getExpectedIncludedResourceResponse works.

Upon further investigation I saw the include path which caused errors was:

product_id.variations.product_id.commerce_product_variation_type

In Commerce Products reference their Variations, and the Variation has a backreference to its Product.

I don't know how it ended up with commerce_product_variation_type instead of commerce_product_type (the proper public field name.)

Gabe helped rubber duck this with me. The problem is JSON:API auto alaises type to {entity_type_id}_type because type is a reserved word in the spec.

Drupal core doesn't have multiple entities that regularly reference themselves where "bundle" => "type". But Commerce does. In fact all of our entities have their bundle key as type.

          // @todo this is where it gets weird.
          // variation -> type (bundle ref)
          // product -> type (bundle ref)
          // store -> type (bundle ref)
          // jsonapi auto aliases `type` to `{entity_type_id}_type`
          $internal_field_name = $resource_type->getInternalName($field_name);

Throughout ResourceTestBase the $this->resourceType resource type is invoked to get an internal field name for a public field. The problem is that the entity being inspected is changing and not of that resource type.