Is your feature request related to a problem? Please describe.
I have a project that is split to multiple sub-projects that share a common set of data.
Each sub-project includes a docker-compose.yml for setting things up.
To include the shared data, I would like to do this in docker-compose.yml:

services:
  myservice:
    build:
      context: .
      additional_contexts:
        data: ../data

And then in Dockerfile for myservice:

COPY --from=data somedata.json /data/somedata.json

But, when I run podman-compose, I see this:

[4/4] STEP 4/8: COPY --from=data somedata.json /data/somedata.json
? Please select an image: 
  ▸ registry.fedoraproject.org/data:latest
    registry.access.redhat.com/data:latest
    docker.io/library/data:latest
    quay.io/data:latest

Describe the solution you'd like
Implement additional_contexts from the Compose Specification.

Describe alternatives you've considered

1. Use Docker Compose instead, which implements that feature.
2. Restructure my project so that each subproject contains a copy of the data directory,
   or copy the data to sub-projects folder in a preparatory build step.
   This would work, but requires restructuring the project even though additional_contexts is part of the Compose Specification.

Additional context
Yes, please! 😁