Create record response with new associations fix

Associations aren't hooked up correctly when the json returned from a create sideloads records that the client doesn't know about yet.  Their `belongsTo` will point at a duplicate of the original object returned from the `createRecord` call.  The original record did not get its `id` set in time for the child records to find it during normalization.

see the test in 6395fe046f15501cc27c5913165871cb87950b78

paired with @denisnazarov 

If this approach is acceptable I can clean up things like updating comments on methods whose signatures changed.