`auto_now` field does not get updated on `model.save(update_fields=[])` if it is not included in `update_fields`

[itzNikshit]

Hi there,
I am a bit new to tortoise-orm and was playing with things where I encountered a problem where an auto_now=True datetimefield does not get updated if I call model.save(update_fields=['updated_field']). It only gets updated if I pass the auto_now field in update_fileds. I don't know if this was intentional or a miss or just that's how things work.

[Prof1-web]

auto_now it's default value for the field. You shouldn't pass this field to update_fields, if you want automatic updating

[itzNikshit]

auto_now it's default value for the field. You shouldn't pass this field to update_fields, if you want automatic updating

But if I don't pass it in update_fields, the updated_at doesn't update on .save()

[Br1an67]

I'd like to work on this. The fix automatically includes auto_now fields in update_fields during save(), matching Django's behavior.

PR: #2122

[itzNikshit]

Thanks for the update @Br1an67 . I had a query on the changes you did, so I added a comment in the PR. Let me know your thoughts on that.