Check compatability with JSON-API 1.1

[Art4]

We only supporting JSON-API 1.0 at the moment. The goals for our librariy are among others:

• ✔️ Be 100% JSON API spec conform
• ✔️ Be open for new spec versions

So we should check if we are open for JSON-API 1.1 or if we have some errors parsing a JSON-API 1.1 document.