[6.1-oldstable] IntegrityError when a customer changes his email address and create a new account with the first email

revision-id: <email address hidden>

It happens when:
 1. Customer A creates an account on Magento. It uses the e-mail "<email address hidden>"
 2. Customer A is imported in OpenERP with the email "<email address hidden>"
 3. Customer A changes his email on Magento to "<email address hidden>"
    * OpenERP still knows the email "<email address hidden>" for customer A
 4. Customer A forget his password and creates a new account on Magento
    with the email "<email address hidden>"
 5. Customer A orders some stuff on Magento with his new account
    * OpenERP import the sale order.
      It doesn't know the customer, but in such case, it tries to find
      an existing record with the same email.
      It finds the first account of customer A and rebind it with the new Magento account
      (instead of creating a new partner).
      A duplicate key error is thrown because only 1 Magento customer is allowed
      for 1 OpenERP partner.

Traceback with some slight changes on the path to shorten it.

2012-11-26 14:00:19,759 4344 ERROR ? openerp.addons.base_external_referentials.external_osv: error in _import of {'store_id': '1', 'website_id': '1', 'updated_at': '2012-11-21 09:12:33', 'prefix': None, 'created_in': u'English', 'password_hash': 'e4672724ce98cad7d892b99970aac2f8:Uu', 'taxvat': 'FR', 'increment_id': '', 'default_billing': '33006', 'tax_class_id': '3', 'customer_id': '31064', 'default_shipping': '33006', 'email': '<email address hidden>', 'confirmation': None, 'firstname': 'Homer', 'middlename': None, 'lastname': 'SIMPSON', 'dob': None, 'gender': None, 'created_at': '2012-11-21 09:11:01', 'suffix': None, 'group_id': '1', 'external_id': '31064'} with external_id 1. Creating report
Traceback (most recent call last):
  File "/srv/openerp/src/server/openerp/addons/base_external_referentials/external_osv.py", line 548, in _ext_import_one_cr
    context=import_ctx)
  File "/srv/openerp/src/server/openerp/addons/base_external_referentials/external_osv.py", line 498, in _ext_import_one
    self.create_external_id_vals(cr, uid, existing_rec_id, external_id, referential_id, context=context)
  File "/srv/openerp/src/server/openerp/addons/base_external_referentials/external_osv.py", line 917, in create_external_id_vals
    return self.pool.get('ir.model.data').create(cr, uid, ir_model_data_vals, context=context)
  File "/srv/openerp/src/server/openerp/osv/orm.py", line 4179, in create
    cr.execute('insert into "'+self._table+'" (id'+upd0+") values ("+str(id_new)+upd1+')', tuple(upd2))
  File "/srv/openerp/src/server/openerp/sql_db.py", line 152, in wrapper
    return f(self, *args, **kwargs)
  File "/srv/openerp/src/server/openerp/sql_db.py", line 212, in execute
    res = self._obj.execute(query, params)
IntegrityError: duplicate key value violates unique constraint "ir_model_data_external_reference_uniq_per_object"
DETAIL: Key (model, res_id, external_referential_id)=(res.partner, 7204, 1) already exists

To solve this issue, we have to never bind new Magento accounts to already bound partners.
We should bind a new Magento account only if a partner with the same email is found,
but is not already bound to a Magento customer.

(By bound, I means linked with Magento customer)

It should be as simple as:

=== modified file 'magentoerpconnect/partner.py'
--- magentoerpconnect/partner.py2012-05-21 05:43:21 +0000
+++ magentoerpconnect/partner.py2012-11-27 13:44:15 +0000
@@ -312,7 +312,7 @@
             cr,cr uid,
             vals['emailid'],
             vals.get('website_id', False),
- is_bound=None,
+ is_bound=False,
             context=context)

         return False, partner_id

BUT, we'll have issues with the following unique constraint, because we'll have 2 accounts with the same email and website...

    _sql_constraints = [('emailid_uniq', 'unique(emailid, website_id)', 'A partner already exists with this email address on the selected website.')]

The last and the better option would be to allows to have 1 partner
for multiple customers on Magento, but so far I do not measure the consequences.
And as the ir_model_data table is shared for all the external ids, we can't actually
remove the ir_model_data_external_reference_uniq_per_object constraint.