code: public HttpAuthServiceBuilder add(Authorizer<HttpRequest> authorizer) {
          requireNonNull(authorizer, "authorizer");
          if (this.authorizer == null) {
              this.authorizer = authorizer;
          } else {
              this.authorizer = this.authorizer.orElse(authorizer);
          }
          return this;
      }
docs: Adds an {@link Authorizer}.