group by parent_id/id does not work as intended #38
Description
When importing partners with their parent partner, using group by parent_id/id as suggested in the documentation can result in multiple parent partners being created, on Odoo 16 at least
The line for the parent partner is not grouped with the child partners as it has an empty parent_id/id column -> it is going to be imported by a different worker. If this worker is working in parallel with a worker importing the children partners, we get the parent partner multiple times, as on Odoo 16 this does not generate a concurrent update error.
Workaround: import in 2 passes, first one uses --ignore=parent_id/id and the second one with that column.