Lists the custom field definitions applicable to an entity of a model.

Returns the deduplicated, ordered union of the model-wide definitions and the owner-scoped definitions matching the entity's scope owners — the same resolution the UI performs when it renders the entity's form. Pass one scope query parameter per owner the entity is attached to, in the compact form ownerType:ownerId[:depth] (e.g. ?scope=EquipmentCategory:42). No scope parameter: only model-wide definitions are returned. Labels (designation) are resolved for the request culture.