[FIX] sale_payment: move method in right module

Commit 8911be11d1 moved code from website_portal_sale to
a new sale_payment module, in order to move code down and ease its use in
variou addons. However a called method was forgotten in the process leading
to some issues when using sale_payment. This commit fixes that.

addons/sale_payment/models/sale_order.py

@@ -9,3 +9,10 @@ class SaleOrder(models.Model):
 
     payment_tx_id = fields.Many2one('payment.transaction', string='Last Transaction', copy=False)
     payment_acquirer_id = fields.Many2one('payment.acquirer', string='Payment Acquirer', related='payment_tx_id.acquirer_id', store=True)
+
+    def _force_lines_to_invoice_policy_order(self):
+        for line in self.order_line:
+            if self.state in ['sale', 'done']:
+                line.qty_to_invoice = line.product_uom_qty - line.qty_invoiced
+            else:
+                line.qty_to_invoice = 0

addons/website_portal_sale/models/sale_order.py

@@ -56,13 +56,6 @@ class SaleOrder(models.Model):
 
         return groups
 
-    def _force_lines_to_invoice_policy_order(self):
-        for line in self.order_line:
-            if self.state in ['sale', 'done']:
-                line.qty_to_invoice = line.product_uom_qty - line.qty_invoiced
-            else:
-                line.qty_to_invoice = 0
-
     @api.multi
     def get_signup_url(self):
         self.ensure_one()