cubicweb #2437859 Avoid concurent changes overwrite [done]

We add a timestamp to edition forms at generation time so that to detect concurent changes and avoid them at validation time

prioritynormal
typeenhancement
done in3.20.0
load0.500
load left0.000
closed by#984505da8b89 [forms] closes #2437859 - Detect and prevent concurrent edition of the same entity.
patch[forms] closes #2437859 - Detect and prevent concurrent edition of the same entity. [applied]