cubicweb-timesheet #1459808 todo by column not correctly displayed on workorder primary view [validation pending]

see e.g. entity 91700 in our internal activites instance (and compare with edition view)

priorityimportant
typebug
done in0.5.2
load left0.000
closed by#9bcd03faebd5 [entities] closes #1459808: use todo_by to implement IMileStone.contractors() for (Work)Order