Redirect unknown ACME challenges to the GitLab instance
This is alternative implementation of !109 (diffs) as being discussed in #165 (comment 155998342)
It redirects all requests to .well-known/acme-challenge/*
to GitLab unless domain's project has requested acme challenge in place
Part of https://gitlab.com/gitlab-org/gitlab-ce/issues/28996
Edited by Nick Thomas