Setup TestKit project to facilitate testing

[remmeier]

There should be an automated test that checks for each type:

• fetching the first x resources
• fetching a single single resource by id
• check all relationship links
• check sorting for all sortable fields
• check filtering for all filterable fields
• check inclusions for all relationships
• check fields for a resource
• check paging

a report should be generated with all the findings.

out of scope: updates, typically requires business know-how that is hard to automate.