async createPermissionGroup (name, rule) {
    await db('permission_groups').insert({
      name,
      rule: JSON.stringify(rule),
      createTime: (new Date()).getTime(),
      updateTime: (new Date()).getTime()
    })

    return true
  }
Create permission group

@param {String} name group name
@param {Object} rule group rule

@returns {Boolean} true