Mark M2M records for addition in parent after they're saved

Closes #12832
(grafted from 4e8ff04aef3a2bfd175e2c77db1421810adc5159)

--HG--
branch : 7.0

sao/src/view/form.js

@@ -4071,8 +4071,12 @@ function eval_pyson(value){
             const callback = result => {
                 if (result) {
                     screen.current_record.save().done(() => {
+                        var added = 'id' in this.screen.current_record.modified_fields;
                         // Force a reload on next display
                         this.screen.current_record.cancel();
+                        if (added) {
+                            this.screen.current_record.modified_fields.id = true;
+                        }
                     });
                 }
             };

tryton/tryton/gui/window/view_form/view/form_gtk/many2many.py

@@ -224,8 +224,11 @@ class Many2Many(Widget):
         def callback(result):
             if result:
                 screen.current_record.save()
+                added = 'id' in self.screen.current_record.modified_fields
                 # Force a reload on next display
                 self.screen.current_record.cancel()
+                if added:
+                    self.screen.current_record.modified_fields.setdefault('id')
                 # Force a display to clear the CellCache
                 self.screen.display()
         WinForm(screen, callback)