pretty clear now that the ONLY difference
rendering a `user` with `include: 'posts.comments'`
is that the included post's user relationship
in jsonapirb is `meta: { included: false }`
and AMS is `data: { id: 1, type: users}`
which I guess is to avoid the user's
post's comment from looking up the user?
similarly, the included comment's post relationship
for jsonapi-rb is `meta: { included: false}`
and AMS is `data: { id: 2, type: posts }`
took a bit of jq and diff to figure this out