Add OpenBao service

Ref: https://gitlab.com/gitlab-org/gitlab/-/issues/468922

What does this merge request do and why?

This MR adds OpenBao as a service in order to facilitate the development of our native Gitlab Secrets Manager.

How to set up and validate locally

1. Check out this branch morefice/add-openbao-service
2. Stop your GDK
3. Run gdk config set openbao.enabled true
4. Run gdk reconfigure
5. Run gdk start openbao

➜  gitlab-development-kit git:(morefice/add-openbao-service) ✗ gdk tail openbao
2024-06-27_06:49:01.28864 openbao               :     $ export BAO_ADDR='http://127.0.0.1:8200'
2024-06-27_06:49:01.28864 openbao               :
2024-06-27_06:49:01.28865 openbao               : The unseal key and root token are displayed below in case you want to
2024-06-27_06:49:01.28865 openbao               : seal/unseal the Vault or re-authenticate.
2024-06-27_06:49:01.28866 openbao               :
2024-06-27_06:49:01.28866 openbao               : Unseal Key: foXG1k....................
2024-06-27_06:49:01.28866 openbao               : Root Token: dev-only-token
2024-06-27_06:49:01.28867 openbao               :
2024-06-27_06:49:01.28868 openbao               : Development mode should NOT be used in production installations!
2024-06-27_06:49:01.28868 openbao               :

Impacted categories

The following categories relate to this merge request:

• gdk-reliability - e.g. When a GDK action fails to complete.
• gdk-usability - e.g. Improvements or suggestions around how the GDK functions.
• gdk-performance - e.g. When a GDK action is slow or times out.

Merge request checklist

• This change is backward compatible. If not, please include steps to communicate to our users.
• Tests added for new functionality. If not, please raise an issue to follow-up.
• Documentation added/updated, if needed.
• Announcement added, if change is notable.
• gdk doctor test added, if needed.
• Add the ~highlight label if this MR should be included in the CHANGELOG.md.