[FIX] payment: save credit card

- Set a payment provider with:
'Save Cards': 'Always'
'Payment Flow': 'Redirection to the acquirer website'
- Process an order on the eCommerce

The payment token is not saved.

The `save_token` value is based on the checkbox which is only added in
'ask' mode:

https://github.com/odoo/odoo/blob/4b8f72eb2315e675ca6d5a0d0961272fc024c475/addons/payment/static/src/js/payment_form.js#L162

We hide and pre-check the checkbox in this case.

opw-2008441
opw-2008275

closes odoo/odoo#34106

Signed-off-by: Nicolas Martinelli (nim) <nim@odoo.com>

addons/payment/views/payment_templates.xml

@@ -87,6 +87,9 @@
                                 <input type="checkbox" name="o_payment_form_save_token" data-remove-me=""/>
                                 Save my payment data
                             </label>
+                            <t t-if="acq.save_token == 'always'">
+                                <input type="checkbox" name="o_payment_form_save_token" checked="'checked'" class="o_hidden" data-remove-me=""/>
+                            </t>
                         </div>
                     </t>
                     <t t-else="acq.payment_flow == 's2s'">