message: Generate default issuer identifier from app name, version and server hostname
diff: const request = require('request')
  const colors = require('colors/safe')
  const logger = require('../lib/logger')
  +const utils = require('../lib/utils')
  +const os = require('os')
  +const config = require('config')
  exports.notify = (challenge) => {
  request.post(process.env.WEBHOOK_URL, {
  json: {
  solution:
  {
  - issuer: process.env.ISSUER_TOKEN || null,
  + issuer: process.env.ISSUER_ID || `${config.get('application.customMetricsPrefix')}-${utils.version()}@${os.hostname()}`,
  recipient: process.env.RECIPIENT_ID || null,
  challenge: challenge.key,
  evidence: null,
  issuedOn: new Date().toISOString()
  },
  signature: null,
  - verifyUrl: null
  + verification: null
  }
  }, (error, res) => {
  if (error) {
  