Feature/in modifier

[kashish2210]

Description

Adds support for expanding token search parameters that use the FHIR :in modifier, for example:

GET /Medication?code:in={valueseturl}

The change introduces a query parameter expansion step before search option parsing. When a token search parameter uses :in, the server expands the referenced ValueSet through the terminology service and rewrites the search parameter into equivalent token values. Non-token parameters are left unchanged.

This supports extensional ValueSet scenarios where clients need to retrieve resources whose coded values are members of a ValueSet.

Related issues

Addresses #4694.
AB#85030

Testing

Validated locally with focused R4 unit test coverage:

dotnet build src\Microsoft.Health.Fhir.R4.Core.UnitTests\Microsoft.Health.Fhir.R4.Core.UnitTests.csproj -f net9.0 --no-restore -m:1

src\Microsoft.Health.Fhir.R4.Core.UnitTests\bin\Debug\net9.0\Microsoft.Health.Fhir.R4.Core.UnitTests.exe --filter FullyQualifiedName~SearchServiceTests.GivenSearchingWithQueryParameterExpander_WhenSearched_ThenExpandedQueryParametersAreUsed --no-progress

Result: passed, 1/1.

src\Microsoft.Health.Fhir.R4.Core.UnitTests\bin\Debug\net9.0\Microsoft.Health.Fhir.R4.Core.UnitTests.exe --filter FullyQualifiedName~SearchParameterValueSetExpanderTests --no-progress

Result: passed, 2/2.

FHIR Team Checklist

• Update the title of the PR to be succinct and less than 65 characters
• Add a milestone to the PR for the sprint that it is merged (i.e. add S47)
• Tag the PR with the type of update: New-Feature
• Tag the PR with Azure API for FHIR and Azure Healthcare APIs because this changes common search behavior used by CosmosDB and SQL paths.
• Tag the PR with Schema Version unchanged because this does not add or update SQL scripts.
• No ADR included; this is a scoped search behavior addition and does not change storage schema or broader system design assumptions.
• CI is green before merge
• Review squash-merge requirements

Semver Change (docs)

Feature

[kashish2210]

@microsoft-github-policy-service agree

[kashish2210]

Hi maintainers, I am an external student contributor and do not have permission to add labels or milestones. Could you please help apply the required PR metadata?

Suggested labels:

• New-Feature
• Azure API for FHIR
• Azure Healthcare APIs
• No-PaaS-breaking-change
• No-ADR

Suggested milestone:

• Current sprint milestone

DevOps item:

• AB#85030

This PR addresses #4694.