code: public LoginResult login(LoginRequest request) {
  
  		ObjectNode body = JsonNodeFactory.instance.objectNode()
  				.put("serviceId", request.getServiceId())
  				.put("userId", request.getUserId());
  
  		HttpPost post = createHttpPost(
  				Gs2Constant.ENDPOINT_HOST + "/login",
  				credential,
  				ENDPOINT,
  				LoginRequest.Constant.MODULE,
  				LoginRequest.Constant.FUNCTION,
  				body.toString());
          if(request.getRequestId() != null) {
              post.setHeader("X-GS2-REQUEST-ID", request.getRequestId());
          }
  
  
  		return doRequest(post, LoginResult.class);
  
  	}
docs: ログイン処理を実行します<br>
  <br>
  
  @param request リクエストパラメータ
  
  @return 結果