stage-in/stage-out from HPC

[kosarko]

We need to download data (incl restricted) into (stage-in) a computational cluster (there might be some wait time before resources are available, expect a non-interactive session)
We need to add data from computational cluster to a repository workspace/workflow/item (or create a new one). This will be one of the last steps of a computational workflow definition (ie. again non interactive).

As a first MVP one possible solution is that the user generates some sort of token(s) and uses these in the workflow (perhaps one of the modes in "Optimize uploads/downloads" might be useful).
At some later point e-infra aai might be involved.

The lifetime of the tokens is expected to be in order of days (should be configurable at least on a global level)

[stranak]

See my comment at #1151. I would wait with this for the situation with OS II AI sub-project to clarify.