US Core Variance Request: eCR / US Core Gender Identity extension

So this isn't strictly a variance request as there is no error/warning that pops up in IG Publisher validation for eCR for Gender Identity (because we are NOT using the latest version of US Core), more of a heads-up that this is what we are doing and that there is an issue with the latest US Core Gender Identity extension.

The recent updates to the eCR IGs were going to use the latest Gender Identity template (from C-CDA Companion Guide) for the CDA version of the IG and the latest US Core Gender Identity extension (from US Core) for the FHIR version of the IG so that we could align with the Gender Harmony project work.

We used the C-CDA Companion Guide Gender Identity template in the CDA IG with no issues, however when we came to use the US Core Gender Identity extension, we realized that there is no way to record more than one gender identity and no way to add a time period (i.e. it doesn't align with the CDA template).

We have thus created a new Gender Identity template (http://build.fhir.org/ig/HL7/case-reporting/StructureDefinition-us-ph-genderidentity-extension.html) that is modeled after the FHIR R5 draft individual-genderIdentity (http://hl7.org/fhir/StructureDefinition/individual-genderIdentity) as it contains the needed cardinality and period.

I've raised a Jira against the US Core specification for this issue - it's linked in the related issues field.