Update HL7 to FHIR mappings with DT datatype to use hl7v2-date extension

[jack-h-wang]

User Story

As a HL7 receiver, I want to have the maximum amount of data that is transmitted by senders, so that the data I receive is accurate and complete.

Description/Use Case

The IN1 mappings implemented a new extension, hl7v2-date, which is designed to store native HL7v2 date values (the DT datatype). We should extend the use of this extension to existing mappings, which may currently be using hl7v2-date-time. This will simplify operations involving datetime values but not date values (such as timezone conversions).

We should also take this opportunity to clean up date handling to make it consistent if any inconsistencies are found.

Risks/Impacts/Considerations

If any FHIR senders are currently using the hl7v2-date-time extension, they should also be informed of the hl7v2-date extension. The FHIR -> HL7v2 mapping will handle either extension, so this is strictly for the case where we want to separate date values from datetime values.

Dev Notes

Acceptance Criteria

• Existing HL7 to FHIR mappings are updated so DT values are represented with the hl7v2-date extension.
• RS FHIR extension glossary is updated.

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