I have a new custom model defined like this

class Customer(models.Model):
    _name = "my_module.customer"
    _inherits = {"res.partner": "partner_id"}
    partner_id = fields.Many2one(comodel_name="res.partner", ondelete="restrict", required=True)
    # more fields...

I have some records in the database (customer and the linked partner). Also the partner records are also linked to portal users (res.users)

Now, I want to remove the partner_id field on my custom model but when i try to upgrade I get a foreign key violation error

psycopg2.errors.ForeignKeyViolation: update or delete on table "res_partner" violates foreign key constraint "res_users_partner_id_fkey" on table "res_users"

The error makes perfect sense since the res.partner record is still referenced in res.users. What I do not understand is why odoo is trying to delete the res.partner record linked to my_module.customer instead of simply unlinking and dropping the partner_id column. Does a Many2one field field behave differently when using delegation?

Any ideas on how I would successfully remove the partner_id field from my_module.customer and leave res.partner and res.users intact?