Workspaces Dockerize collaborators into the same image

[mrrr3d]

Is your feature request related to a problem? Please describe.
I want to run openfl containers in muti-cluster environmet, but I need to build images for every collaborator, because collaborators have different plans.

Describe the solution you'd like
Maybe we can mount the plan directory like certs.tar when starting the container, like this:

docker run --rm \
  --network host \
  --mount type=bind,source=./certs.tar,target=/certs.tar \
  --mount type=bind,source=./plan,target=/workspace/plan \
  example_workspace bash -c "fx aggregator start ..."

Thanks!