cubicweb-celerytask #16640666 Add support for parent_task weaving in celery-monitor [validation pending]

so that subtasks (ie. tasksk that spawn tasks) are linked via this parent_task relation.

prioritynormal
typeenhancement
done in0.3.0
load left0.000
closed by#378002d47604 [entities] try to weave 'parent_task' relations between CelereyTask entities (closes #16640666)
patch[entities] try to weave 'parent_task' relations between CelereyTask entities (closes #16640666) [applied]