Handle multiple target types for ReferenceSearchParam

[feordin]

Description

Updates SQL generator to handle multiple target types for ReferenceSearchParam.

Related issues

Addresses [issue AB#177046].

Testing

Describe how this change was tested.

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: Bug, Build, Dependencies, Enhancement, New-Feature or Documentation
• Tag the PR with Open source, Azure API for FHIR (CosmosDB or common code) or Azure Healthcare APIs (SQL or common code) to specify where this change is intended to be released.
• Tag the PR with Schema Version backward compatible or Schema Version backward incompatible or Schema Version unchanged if this adds or updates Sql script which is/is not backward compatible with the code.
• When changing or adding behavior, if your code modifies the system design or changes design assumptions, please create and include an ADR.
• CI is green before merge
• Review squash-merge requirements

Semver Change (docs)

Patch|Skip|Feature|Breaking (reason)

In general, to fix a "useless assignment to local variable" where you still need the side effect of the right-hand side, you remove the unused local variable and keep just the expression statement (method call). If you do not need the side effect either, you remove the entire statement.

Here, the test clearly needs to execute _queryGenerator.VisitSqlRoot(sqlExpression, searchOptions) to populate _strBuilder, because generatedSql is read from _strBuilder immediately afterward. However, the variable output is never used. The best fix is therefore to remove the var output = part and keep the method call as a standalone statement. This preserves all existing behavior and cleans up the unused assignment.

Concretely, in src/Microsoft.Health.Fhir.SqlServer.UnitTests/Features/Search/SqlQueryGeneratorTests.cs, replace the line:

185:         var output = _queryGenerator.VisitSqlRoot(sqlExpression, searchOptions);

with:

185:         _queryGenerator.VisitSqlRoot(sqlExpression, searchOptions);

No additional methods, imports, or definitions are needed.

[feordin]

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