Artifact repository agnostic key-only artifacts

[Bobgy]

Summary

I was looking at the new key-only artifact support: #4618.
It looks awesome and very useful.

However, it seems to me that there's a missing piece. A workflow may use key-only artifacts like the example:
https://github.com/argoproj/argo/blob/master/examples/key-only-artifact.yaml

...
          artifacts:
          - name: file
            path: /mnt/file
            s3:
              key: my-file
...

However, the definition is still tied to s3. I think it helps if the definition can be artifact repository agnostic, for example

          artifacts:
          - name: file
            path: /mnt/file
            genericKey: my-file

Use Cases

The same workflow definition would be agnostic to choice of artifact repository store, it can be s3, gcs, oss, and maybe hdfs (if path is mapped to key).

Note, I do not have plans to use this feature yet, but it may making key-only artifacts more useful that I can consider in the future.

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[alexec]

Nice idea. Would you like to submit a PR?

[Bobgy]

Thanks for confirming this makes sense to you too.

For my schedule, not yet right now. When I get to the point I need this in a short term, I will consider contributing it.