Make $merge Feature Optional / Disable Merge Services When Not Needed #890
Description
Summary
When configuring supported_resource_types in the HAPI FHIR JPA Starter to include only a subset of resources (e.g., Organization, HealthcareService), the application fails to start due to the $merge feature being initialized unconditionally. The merge services assume the existence of a Patient DAO, which is not present when the user explicitly limits supported resources.
This results in startup failures such as:
No DAO exists for resource type class org.hl7.fhir.r4.model.Patient
This makes it impossible to run a minimal JPA server without implicitly supporting Patient or other resources that $merge depends on.
Expected Behavior
- It should be possible to disable all $merge-related services (MergeValidationService, ResourceMergeService, MergeProvenanceSvc, and merge providers).
- When disabled, no merge-related beans should be constructed and the server should start even if Patient is not available in the DaoRegistry.
- Configuration should remain fully backward-compatible.