Consider whether we want to change our current approach to dates

[mikix]

Right now, we have a list of date fields we check in priority order, for when we want to slice by a resource date.

This ticket is just a reminder of our "philosophy" around that priority order and a discussion check-in on whether that approach makes sense.

Here's what we are currently thinking, in highest preference first order:

1. Date of health system interaction (e.g. DiagnosticReport.effectiveDateTime)
2. Administrative date (i.e. resource creation date like DiagnosticReport.issued)
3. Clinically relevant "start" date (e.g. Condition.onsetPeriod.start)

And stop there (i.e. no Condition.onsetPeriod.end or Condition.abatementDateTime)

Thoughts? This should maybe go in the documentation once we bless it.

[mikix]

The qualifier repo was recently updated to include .end fields and abatement - just in general, it recommends more fields. And I've got a PR to implement that in #29, so let's consider this considered and close this ticket.