code: async function create(ctx) {
    let { Model } = ctx.state;
    let code = Model.api.create;
    if (code > _alaska.PUBLIC && !ctx.user) {
      //未登录,需要认证
      ctx.status = 401;
      return;
    }
    let doc = new Model(ctx.state.body || ctx.request.body);
    if (code > _alaska.PUBLIC) {
      let { userField } = Model.userField;
      // $Flow 已经确认ctx.user存在
      doc.set(userField, ctx.user._id);
    }
    await doc.save();
    ctx.state.record = doc;
    ctx.body = doc.data('create');
  }
docs: 创建一个对象