[FIX] payment: unique reference constraint

The payment transactions references must be unique, but for
states within draft, pending, done states, not
if the transaction has been canceled or in error.

Otherwise, this is not possible to create a new payment
transaction for an ecommerce order for which
the payment has been canceled by the acquirer

For instance, when the customer lands on Ogone,
then hit the cancel button

opw-627914

addons/payment/models/payment_acquirer.py

@@ -371,8 +371,15 @@ class PaymentTransaction(osv.Model):
                                          help='Reference of the customer in the acquirer database'),
     }
 
-    _sql_constraints = [
-        ('reference_uniq', 'UNIQUE(reference)', 'The payment transaction reference must be unique!'),
+    def _check_reference(self, cr, uid, ids, context=None):
+        transaction = self.browse(cr, uid, ids[0], context=context)
+        if transaction.state not in ['cancel', 'error']:
+            if self.search(cr, uid, [('reference', '=', transaction.reference), ('id', '!=', transaction.id)], context=context, count=True):
+                return False
+        return True
+
+    _constraints = [
+        (_check_reference, 'The payment transaction reference must be unique!', ['reference', 'state']),
     ]
 
     _defaults = {