With the 7.0 model all accounting-related fields are synchronized
from company to contacts (both are res.partner records), so the
unique check is not a trivial unique constraint. It must be updated
to use a *partial unique index* that applies only to "commercial
entities" and not to contacts. The condition for being a commercial
entity is "is_company is true or parent_id is NULL".
If companies have unique vat/nrc numbers, then their contacts
will be consistent because they are automatically synchronized,
so the uniqueness between contacts does not have to be checked.
(The auto-sync is performed by res.partner automatically and covered
by tests in the "base" module)
bzr revid: odo@openerp.com-20130415175258-l15meqin80sbhggu
Olivier Dony
556e4e76c3