code: public JerseyClientBuilder using(ExecutorService executorService, ObjectMapper objectMapper) {
          this.executorService = executorService;
          this.objectMapper = objectMapper;
          return this;
      }
docs: Uses the given {@link ExecutorService} and {@link ObjectMapper}.
  
  @param executorService a thread pool
  @param objectMapper    an object mapper
  @return {@code this}
  @see #using(io.dropwizard.setup.Environment)