[IMP] sale_variant_configurator: add create_product_variant to form

When you try configure a variant that doesn't exist yet, there's no way to create it and add it to the sale order

sale_variant_configurator/views/sale_view.xml

@@ -56,6 +56,12 @@
                         />
                         <field name="price_extra" />
                     </tree>
+                    <field name="can_create_product" invisible="1" />
+                    <field
+                        name="create_product_variant"
+                        attrs="{'invisible':
+                        [('can_create_product', '=', False)]}"
+                    />
                 </field>
             </xpath>
         </field>