Automatically validate Let's Encrypt integration
We don't currently do any automated testing on this, and this caused us to miss an issue in #4343 (closed). We should setup an automated process to do this. We do need to be wary of the rate limiting on the Let's Encrypt production server.
- Update our
letsencrypt::enablerecipe so we can run only against staging, and setup a test to verify we can get a certificate just from staging
- Setup a package to verify the nightly package can get a certificate once a day
- Migrate dev.gitlab.org to use Let's Encrypt