As an intermediate step to having our revamped expressions that can address data within lists, we want to provide a yield <field> operator that can unnest already with the new extractor syntax including unnesting with [].
### Definition of Done
- [x] Agree on the syntax to use (for now)
- [x] Implement the operator
As an intermediate step to having our revamped expressions that can address data within lists, we want to provide a
yield <field>operator that can unnest already with the new extractor syntax including unnesting with[].