[FIX] sale: Description of the product 'Downpayment' not translated

When you create a down payment invoice from an SO, the product that is used in the line is 'Down Payment'.
The description of this product, which is visible for the customer, was not translated to the language
of the customer in the SO and in the invoice. It was translated to the language of the user logged.
This fix is made to keep the same behavior for the description of an SO line and for the description
of the invoice line.

opw:1820081

addons/sale/wizard/sale_make_invoice_advance.py

@@ -76,12 +76,14 @@ class SaleAdvancePaymentInv(models.TransientModel):
 
         if self.amount <= 0.00:
             raise UserError(_('The value of the down payment amount must be positive.'))
+        context = {'lang': order.partner_id.lang}
         if self.advance_payment_method == 'percentage':
             amount = order.amount_untaxed * self.amount / 100
             name = _("Down payment of %s%%") % (self.amount,)
         else:
             amount = self.amount
             name = _('Down Payment')
+        del context
         taxes = self.product_id.taxes_id.filtered(lambda r: not order.company_id or r.company_id == order.company_id)
         if order.fiscal_position_id and taxes:
             tax_ids = order.fiscal_position_id.map_tax(taxes).ids
@@ -152,6 +154,7 @@ class SaleAdvancePaymentInv(models.TransientModel):
                     tax_ids = order.fiscal_position_id.map_tax(taxes).ids
                 else:
                     tax_ids = taxes.ids
+                context = {'lang': order.partner_id.lang}
                 so_line = sale_line_obj.create({
                     'name': _('Advance: %s') % (time.strftime('%m %Y'),),
                     'price_unit': amount,
@@ -162,6 +165,7 @@ class SaleAdvancePaymentInv(models.TransientModel):
                     'product_id': self.product_id.id,
                     'tax_id': [(6, 0, tax_ids)],
                 })
+                del context
                 self._create_invoice(order, so_line, amount)
         if self._context.get('open_invoices', False):
             return sale_orders.action_view_invoice()