R4/R4B: Support R5 backport extension-ValueSet.expansion.property and correct score source (ordinalValue/itemWeight should not be on expansion)

[patrick-werner]

Description

LForms currently supports score extraction from ValueSet.expansion.contains[*].extension using ordinalValue/itemWeight.
While practical, this is not the correct modeling approach: ordinalValue and itemWeight should not be applied directly on expansion.contains.

Instead, the R5 mechanism via ValueSet.expansion.contains.property should be used, including the backport extension for earlier FHIR versions:

• http://hl7.org/fhir/5.0/StructureDefinition/extension-ValueSet.expansion.contains.property

Goal

1. Parse the R5 backport extension and map score values to answer.score.
2. Stop treating ordinalValue/itemWeight on expansion.contains[*].extension as the primary/recommended approach.

Current Behavior

• Score is read from expansion.contains[*].extension (ordinalValue/itemWeight).

Expected Behavior

• Primary path: score from expansion.contains[*].property (or backport extension path in R4/R4B).
• Legacy cases with ordinalValue/itemWeight on contains.extension:
  • optionally still read for backward compatibility,
  • but treat as deprecated/fallback and document it clearly.

Implementation Proposal

• Extend the import pipeline to evaluate both native R5 contains.property and the R4/R4B backport extension extension-ValueSet.expansion.property.
• Use this score resolution order:
  1. contains.property / backport property
  2. (optional fallback) contains.extension with ordinalValue/itemWeight
• Update docs (sdc-support.md and related docs/release notes) to clarify that contains.extension is not the normative path.
• Add/adjust tests for:
  • R4/R4B with backport extension
  • R5 with contains.property
  • legacy fallback behavior (if retained)

[patrick-werner]

updated issue to refer to the correct backport extension: http://hl7.org/fhir/5.0/StructureDefinition/extension-ValueSet.expansion.contains.property

[plynchnlm]

Looks good. Does your implementation proposal mean you are planning to implement it?