Establish testing framework to demonstrate integrity and accuracy or aggregated api results

[samiatoui]

[Stephen-ONeil]

What I have in mind is to "can" a set of input data (run synthesizer once, save the json representation), calculate the aggregation for it independently, and then run an integration test that loads that canned input data to FHIR and asserts that the aggregates match the manually calculated values. Simple snapshot test approach, not totally rock solid but good enough for demonstrative purposes in a time crunch.