Client and AsyncClient abstraction seems not good enough

1. we expose much implemention detail to user api , user must identify the sync feign client/builder and the async client/buider.
   If we only expose client to user , and proxy sync/async method accordingly(seperate/implement the async boundary accordingly), is it feasible?

2.sync invoke or async invoke seems is naturally unified, could we just Override accordingly?

public interface Client { 

default Response execute(Request request, Options options) throws IOException {
      return execute(request, options, emptyContext).join(); 
}

default CompletableFuture<Response> execute(Request request, Options options, Optional<C> requestContext){
  return CompletableFuture.completed(execute(request, options));
}

}

Start with the Client and AsyncClient abstractions, then trace the sync and async Feign client/builders and their execute entry points. Compare whether proxying sync and async methods can share one user-facing Client without exposing implementation details. Done means a clear feasibility decision and defined scope for any abstraction change.