cubicweb-timesheet #5537340 ValidateActivitiesAction uses the deprecated user_callback stuff [validation pending]

which is broken when the cw app is delivered by pyramid

priorityimportant
typebug
done in0.13.0
load0.500
load left0.000
closed by#fc05754dcfca [views] replace the use of deprecated (and now broken) user_callback (closes #5537340)
patch[views] factorize ValidateActivitiesAction and ArchiveActivitiesAction (related to #5537340) [applied][views] replace the use of deprecated (and now broken) user_callback (closes #5537340) [applied]