[ref-api] add manufactured_at and warranty_end at cluster level using the oldest node

data/grid5000/sites/grenoble/clusters/dahu/dahu.json

data/grid5000/sites/grenoble/clusters/drac/drac.json

data/grid5000/sites/grenoble/clusters/servan/servan.json

data/grid5000/sites/grenoble/clusters/troll/troll.json

data/grid5000/sites/grenoble/clusters/yeti/yeti.json

data/grid5000/sites/lille/clusters/chiclet/chiclet.json

data/grid5000/sites/lille/clusters/chifflot/chifflot.json

...00/sites/luxembourg/clusters/petitprince/petitprince.json

data/grid5000/sites/lyon/clusters/gemini/gemini.json

data/grid5000/sites/lyon/clusters/hercule/hercule.json

data/grid5000/sites/lyon/clusters/neowise/neowise.json

data/grid5000/sites/lyon/clusters/nova/nova.json

data/grid5000/sites/lyon/clusters/orion/orion.json

data/grid5000/sites/lyon/clusters/pyxis/pyxis.json

data/grid5000/sites/lyon/clusters/sagittaire/sagittaire.json

data/grid5000/sites/lyon/clusters/sirius/sirius.json

data/grid5000/sites/lyon/clusters/taurus/taurus.json

data/grid5000/sites/nancy/clusters/graffiti/graffiti.json

data/grid5000/sites/nancy/clusters/graoully/graoully.json

data/grid5000/sites/nancy/clusters/graphique/graphique.json