As contributor, I can add a group of domains (and not only domains) in a group of domains

Example : "Habillement et prêt à porter" will contain group of domains "Habillement luxe homme" et "habillement luxe mixte + other domains

Please first size it and we ll see

No files, tests, or entry points are named. First clarify the intended hierarchy for groups of domains and what “other domains” means, then size the work against the existing backend API model and its tests. Done should be defined as contributors being able to add nested domain groups with agreed behavior.

Written by the indexing model from the issue text.