This will allow using non-buildpack images to the config and the API, the current proposed config would be:

celery-worker:
  description: celery worker for long-running tasks
  type: continuous 
  build:
    use-prebuilt: python3.11 # refers to docker-registry.tools.wmflabs.org/toolforge-python311-sssd-base:latest
  run:
    command: celery

Adding support for use-prebuilt key in the build section (API + config) and then passing that image to the jobs api when starting the jobs.