text: const qs = require('querystring');
  const _ = require('lodash');
  
  module.exports = function getFormUrl(req) {
    const queryParams = qs.stringify(_.omitBy({
      client_id: req.query.app_id || req.query.client_id,
      redirect_uri: req.query.redirect_uri,
      response_type: req.query.response_type,
      state: req.query.state,
      scope: req.query.scope,
    }, _.isEmpty));
    return `/oauth/authorize?${queryParams}`;
  };
  