Exposing the HAPI-FHIR RestfulClientFactory for config

[MikeRileyGTRI]

A common issue we run up to a lot is that sometimes access to the FHIR server needs a bit of custom configuration, such as custom headers, or some authentication interceptor. We may even have a proxy server in the future. All of these types of client configurations are available in the Apache HTTP client/Hapi fhir HTTP client that CQL-Engine uses. Without having to modify the engine, would it be possible for cqf-ruler to expose the client factory options as configuration?
An easy use case would be a slow fhir server; a server that takes longer than the 5 seconds before timeout, it would be helpful to modify the timeout on the client via configuration without having to change the data providers in the cql-engine itself.