Optionalquery: QueryParamsPerform a GET expecting JSON and parse it into T. The accept header
defaults to application/json but can be overridden per endpoint (e.g. the
search collection serves HAL+JSON and 406s on plain application/json).
Optionalquery: QueryParamsPerform a request with Accept negotiation and transient-error retries.
Build a fully-qualified URL from a path and optional query parameters.