[IMP] web: allow to override the number of buttonbox buttons

See odoo/odoo#31546

closes odoo/odoo#31698

Signed-off-by: Géry Debongnie (ged) <ged@openerp.com>

addons/web/static/src/js/views/form/form_renderer.js

@@ -279,7 +279,7 @@ var FormRenderer = BasicRenderer.extend({
         var visible_buttons = buttons_partition[1];
 
         // Get the unfolded buttons according to window size
-        var nb_buttons = [2, 4, 6, 7][config.device.size_class];
+        var nb_buttons = this._renderButtonBoxNbButtons();
         var unfolded_buttons = visible_buttons.slice(0, nb_buttons).concat(invisible_buttons);
 
         // Get the folded buttons
@@ -318,6 +318,13 @@ var FormRenderer = BasicRenderer.extend({
         this._registerModifiers(node, this.state, $result);
         return $result;
     },
+    /**
+    * @private
+    * @returns {integer}
+    */
+    _renderButtonBoxNbButtons: function () {
+        return [2, 4, 6, 7][config.device.size_class];
+    },
     /**
      * @private
      * @param {Object} node