I am trying to use the MinIO predefined image. docker.io is heavily rate-limited at the location I'm using the crate from. MinIO is also available from Quay at quay.io/minio/minio. Because this is hardcoded in a const variable, I think the only way around this and still use rustainers is to copy all of the code from minio.rs into my project and provide a different value for const MINIO_IMAGE.
Removing the registry name would allow setting the registry via Podman/... configuration outside of rustainers.
Another option is to allow customizing the entire image name via the code, but this is a much deeper change.