message: Don't solve metrics challenge when endpoint is accessed by prometheus scraper
diff: @@ -13,7 +13,10 @@ const Op = models.Sequelize.Op
  exports.serveMetrics = function serveMetrics (reg) {
  return (req, res, next) => {
  - utils.solveIf(challenges.exposedMetricsChallenge, () => { return true })
  + utils.solveIf(challenges.exposedMetricsChallenge, () => {
  + const userAgent = req.headers['user-agent'] || ''
  + return !userAgent.includes('Prometheus')
  + })
  res.set('Content-Type', reg.contentType)
  res.end(reg.metrics())
  }
  