Add integration tests with JSON:API Schema

Here's an initial patch. It'll fail.

This relates to #3109873: Provide a `resource_type` route parameter (e.g. for openapi, jsonapi_schema).

Forgot the patch.

Ah, I forgot I have a patch to fix this: #3093033: TopLevelSchemaLinkProviderBase::getLink breaks on custom route.

JSON:API Schema had a release with the required fix. Rerunning tests

Failure is due to the fact we now have the describedby link

--- Expected
+++ Actual
@@ @@
     'links' => Array (
         'shipping-methods' => Array (...)
         'self' => Array (...)
+        'describedby' => Array (...)
     )
 )

After adding the new link there was an error on the shipping methods route. This information is now in the order meta, so maybe it's not even needed.

Fixed.