Add fhirServerUrl support to enable FHIRPath resolve() function

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Add fhirServerUrl support to enable FHIRPath resolve() function

Is your feature request related to a problem? Please describe.

The @aehrc/sdc-populate package doesn't support the FHIRPath resolve() function. When using expressions like %order.requester.resolve().name.first().family in a questionnaire's initialExpression, the population fails silently and returns empty values.

This is frustrating because resolve() is a standard FHIRPath function that allows questionnaires to populate fields from referenced resources (e.g., getting a Practitioner's name from a ServiceRequest's requester reference) without requiring the calling application to pre-resolve all references manually.

Describe the solution you'd like

Pass fhirServerUrl option to fhirpath.evaluate() calls. According to fhirpath.js documentation, the resolve() function requires this option:

options.fhirServerUrl - a URL pointing to a FHIR RESTful API server that
is used to `resolve()` resources.

The value should come from fetchResourceRequestConfig.sourceServerUrl, which is already available in the codebase. This would require:

1. Threading fetchResourceRequestConfig through functions that call fhirpath.evaluate()
2. Adding fhirServerUrl: sourceServerUrl to the fhirpath options object
3. Updating fhirpath.js dependency to version 4.5.0+ (where resolve() was implemented)

Describe alternatives you've considered (if applicable)

The current workaround is to pre-resolve all referenced resources in the calling application before passing them as separate launch contexts. For example, instead of using %order.requester.resolve(), the application must:

1. Fetch the ServiceRequest
2. Extract the requester reference
3. Fetch the Practitioner
4. Pass it as a separate %practitioner context

This works but requires each application to implement custom pre-resolution logic and questionnaires to be designed around this limitation rather than using standard FHIRPath patterns.

Additional context

• The resolve() function was added to fhirpath.js in version 4.5.0 (2025-07-01)
• Current @aehrc/sdc-populate depends on fhirpath 3.15.2, which doesn't have resolve()
• The change is backwards compatible - if sourceServerUrl is not provided, resolve() simply won't work (same as current behavior)
• I have a working patch implementation and would be happy to submit a PR if this approach is acceptable

Example questionnaire expression that would work after this change:

{
  "linkId": "ordering-physician-name",
  "type": "string",
  "extension": [{
    "url": "http://hl7.org/fhir/uv/sdc/StructureDefinition/sdc-questionnaire-initialExpression",
    "valueExpression": {
      "language": "text/fhirpath",
      "expression": "%order.requester.resolve().name.first().given.first() & ' ' & %order.requester.resolve().name.first().family"
    }
  }]
}