code: function loadUsrInfo(token, app, zlSite, next) {
    app.models.zlUser.findById(token.userId, (err, usr) => {
      if (err) next(err);
      else if (usr) {
        zlSite.user = _.cloneDeep(usr);
        if (!zlSite.user.usrPhoto && zlSite.user.email) {
          // use gravatar
          let graHash = md5(zlSite.user.email.toLowerCase());
          zlSite.user.usrPhoto = `https://www.gravatar.com/avatar/${graHash}?s=100&d=mm`
        }
        next();
      }
      else {
        // user must no longer exist
        next();
      }
    });
  }
docs: load user details into variable