rejects R5-defined parameter

[jmandel]

Bug

On the /r5 endpoint, the R5-defined parameter name system is rejected. Only sourceSystem (the R6 name) is accepted.

Repro

# R5 uses "system" alongside "sourceCode" — REJECTED
curl -s 'https://tx-dev.fhir.org/r5/ConceptMap/$translate?sourceCode=male&system=http://hl7.org/fhir/administrative-gender' \
  -H 'Accept: application/fhir+json'
# Returns 400: "sourceSystem parameter is required when using sourceCode"

# Only "sourceSystem" (R6 name) works
curl -s 'https://tx-dev.fhir.org/r5/ConceptMap/$translate?sourceCode=male&sourceSystem=http://hl7.org/fhir/administrative-gender&targetSystem=http://terminology.hl7.org/CodeSystem/v3-AdministrativeGender' \
  -H 'Accept: application/fhir+json'
# Returns 200

Spec reference

R5 section 6.15.22 defines system (IN, uri) for $translate. R6 renamed this to sourceSystem. The /r5 endpoint should accept the R5 name.