multiple `storageSite`s with `mkNtuples`

Submitting a single set of CRAB jobs with multiple storage sites would be beneficial when the output of possible computing-demanding CRAB jobs should be analysed by collaborators using different clusters (instead of each user resubmitting the same jobs).

Answer by Stefano Belforte: this seems not to be directly possible, however one could to use Rucio.

One should investigate if that could be automated with mkNtuples. We would then ensure that all teams working on the same analysis work with the exact same events in the exact same order.