odoo_source/addons/payment_sips/views/payment_sips_templates.xml

<?xml version="1.0" encoding="utf-8"?>
<odoo>

    <template id="redirect_form">
        <form t-att-action="api_url" method="post">
            <input type="hidden" name="Data" t-att-value="Data"/>
            <input type="hidden" name="InterfaceVersion" t-att-value="InterfaceVersion"/>
            <input type="hidden" name="Seal" t-att-value="Seal"/>
        </form>
    </template>

</odoo>