Setting credentials for s3_v2 driver doesn't work with environment variables

I'm a maintainer for GitLab packaging in NixOS. We are using gitlab container-registry with a S3 backend, currently with s3 (_v1) backend. We configure it with a yml file like so:

storage:
  s3:
    bucket: "stag-gitlab-registry"
    chunksize: 104857600
    region: "does not matter"
    regionendpoint: "http://localhost:7480"
...

together with an environment variable that is required as the config is world-readable in Nix.

REGISTRY_STORAGE_S3_ACCESSKEY=accesskey
REGISTRY_STORAGE_S3_SECRETKEY=secretkey

Because of #1464 (closed) / #1536, it's not possible to set the environment variables

REGISTRY_STORAGE_S3_V2_ACCESSKEY=accesskey
REGISTRY_STORAGE_S3_V2_SECRETKEY=secretkey

Please allow this variables to be set or alternatively allow specifying a file containing the secret in the config. Thank you