Query/Test: add relationship test model which only contains references (no collections)

[maumar]

So we can test scenarios which don't support collections (e.g. non-json complex types)

[roji]

Noting that this doesn't have to be a fully separate model - just move the reference-only tests to a different suite and ignore the collection references, or similar (whatever's simplest basically).

[maumar]

yeah that was my thinking as well