(PDB-1071) Add pagination to service query method

In order to support pagination in the service query method, have it
accept a map instead of the raw query structure.  The map should contain
a :query referring to the original query, alongside (optional)
:order-by, :offset, and :limit members.
There's a notable amount of redundancy between the new test and the one above it (in fact I just started via copy-paste).  Think that's OK for now?