ServerRegistryResourceProvider cache invalidation is problematic in multi-server environments

[JohnTimm]

The ServerRegistryResourceProvider class implements both FHIRRegistryResourceProvider and FHIRPersistenceInterceptor. Registry resources read from the persistence layer are cached in a tenant/datastore specific cache that gets invalidated on afterCreate, afterUpdate, and afterDelete events. Unfortunately this only works if the Create/update/delete was performed through the same server where the cache resides. In multi-server environments some of the nodes may end up with stale data. The caching feature should be removed from the FHIRRegistryResourceProvider or it should be cache with a time-based eviction policy.

[kmbarton423]

created a CodeSystem resource containing code=icecream
GET https://localhost:9443/fhir-server/api/v4/CodeSystem/hungrycaterpillar/$validate-code?code=icecream
immediately updated the CodeSystem removing code=icecream
repeated $validate multiple times to confirm that the cached code was evicted within a minute