move over DNS entry for `ci.concourse-ci.org`

[jamieklassen]

Tentative plans:

Pre-work:

• merge https://github.com/concourse/ci/pull/231
• merge https://github.com/concourse/hush-house/pull/90
• Figure out prod deploys: https://github.com/concourse/prod/issues/45
  • [ ] windows worker on prod should move its config to ci

PR to concourse/prod:

• [x] remove ci-concourse-ci-org-dns from https://github.com/concourse/prod/blob/master/iaas/dns.tf

PR to concourse/ci:

• [x] topgun worker - update configuration in concourse/ci with new DNS
• [x] k8s-topgun worker - update configuration in ci with new DNS
• [x] windows worker - update configuration in ci with new DNS
• [x] concourse-pipeline resource inside the reconfigure pipeline
• [x] slack notification resource inside the main pipeline

PR to concourse/hush-house:

• [x] change concourse-nci-address in https://github.com/concourse/hush-house/blob/master/terraform/main.tf
• [x] external url on the new environment needs to change too
• [x] change cluster name from ci-house to ci

Secrets:

• [x] TLS cert on API/web

manual followup steps:

• [x] terraform apply in prod
• [x] terraform apply in hush-house
• [x] deploy CI and all its worker pools, using the results of #45
• [x] github auth redirect url

[jamieklassen]

potentially TLS certificates need to be updated as well

[vito]

This is done now but it was a bit clunky getting everything up to date. I've created a new epic, Greenpeace, for cleaning up our environments. Let's track high level goals here and try to tackle this some time soon.