nixos/gitlab: Add a warning message

GitLab instances created or updated between versions [15.11.0, 15.11.2]
have an incorrect database schema. [1] This will become a problem once
upgrading GitLab to >=16.2.0.

A workaround can be found in the GitLab docs: [2]

[1]: https://gitlab.com/gitlab-org/gitlab/-/issues/408835
[2]: https://docs.gitlab.com/ee/update/versions/gitlab_16_changes.html#undefined-column-error-upgrading-to-162-or-later

nixos/modules/services/misc/gitlab.nix

···
         ''Support for container registries other than gitlab-container-registry has ended since GitLab 16.0.0 and is scheduled for removal in a future release.
           Please back up your data and migrate to the gitlab-container-registry package.''
       )
+      (mkIf
+        (versionAtLeast (getVersion cfg.packages.gitlab) "16.2.0" && versionOlder (getVersion cfg.packages.gitlab) "16.5.0")
+        ''GitLab instances created or updated between versions [15.11.0, 15.11.2] have an incorrect database schema.
+        Check the upstream documentation for a workaround: https://docs.gitlab.com/ee/update/versions/gitlab_16_changes.html#undefined-column-error-upgrading-to-162-or-later''
+      )
     ];
 
     assertions = [