update spec to use standard systemAction, instead of extension

[isaacvetter]

Following the implementations of this spec, CDS Hooks incorporating a standard systemAction into the CDS Hooks response. This feature will (almost certainly) be published this year in the official HL7 STU2 release of the specification.

I think it makes sense to update this specification to use the standard systemAction element, instead of using an extension.

(Feel free to push back and tell me to write a PR myself ;)).

[mattvarghese]

Also, any thoughts on how to have guardrails so that the systemAction only updates PAMA info and not other info on the orders? Or is that better asked as a CDS Hooks question?

[jmandel]

Agreed @isaacvetter ! Re: updates, you want to share a PR that we can merge when STU2 is published? Or a "work in progress" note to merge sooner?

Re: guardrails, I think they're important and narrative based, but I'd be happy to include narrative in this spec if you want to propose lagnuage @mattvarghese

(For the broader question of how to provide guardrails and whether they can/should be computable, we should discuss in CDS Hooks)

[cfeltner]

Since this specification is already in use on production systems, I think it is important to maintain backwards compatibility. Therefore, I would suggest still allowing the extension but indicate the standard SystemAction be used in future implementations.