Search integration tests

WIP for adding more integration tests around search.

- [x] with restricted attributes
- [x] with filter string
- [x] with filter object
- [ ] with size limit (failing test)
- [x] attributes_only
- [ ] deref (don't know how to test this)
- [ ] scope (needs additional fixtures)

cc @mtodd @schaary 
See my note below, but this will fail until we treat `sizeLimitExceeded` (and `timeLimitExceeded`) as a non-error/successful search response.