Add HTTPS PROXY V2 Support for GitLab Pages

What does this MR do?

Brings in the ability to support GitLab Pages in the endevour for PROXY V2 Support. This was implemented in GitLab Pages via: gitlab-org/gitlab-pages!278 (merged)

This updates our Helm chart to support this option.

Testing

Use the below to enable the appropriate option:

global:
  pages:
    enabled: true
    externalHttps:
      - 1.1.1.1
gitlab:
  gitlab-pages:
    statusUri: "/-/readiness"
    useProxyV2: true

You can then validate that the Service Object created only allows PROXYv2 traffic. And we can now hit the status URI via curl. An example curl command, via the use of port-forwarding:

kubectl port-forward svc/<release_name>-gitlab-pages-custom-domains 8443:443

curl -k https://127.0.0.1:8443/-/readiness --haproxy-protocol

Related issues

Addresses: #2823 (closed)

Checklist

See Definition of done.

For anything in this list which will not be completed, please provide a reason in the MR discussion.

Required

• Merge Request Title and Description are up to date, accurate, and descriptive
• MR targeting the appropriate branch
• MR has a green pipeline on GitLab.com

Expected (please provide an explanation if not completing)

• Test plan indicating conditions for success has been posted and passes
• Documentation created/updated
• Tests added
• Integration tests added to GitLab QA
• Equivalent MR/issue for omnibus-gitlab opened