Add file de-duplication #29
Description
Some workflows upload files as input which were outputs of other workflows. This enables the parent / child detection feature to work
However, storage of identical objects is duplicated. This could be improved (a bit like git forks on github and gitlab but a lot simpler since there is only a single server).
Some attempt was made, but not merged I think.
Similar approach could be done for IMAS data but might need to based on IMAS checksums, not file checksums.