Gets the FHIR capability statement (STU3, R4, R5), or the conformance statement in the DSTU2 case for the store, which contains a description of functionality supported by the server. Implements the FHIR standard capabilities interaction (STU3, R4, R5), or the conformance interaction in the DSTU2 case. On success, the response body contains a JSON-encoded representation of a CapabilityStatement resource.