[4981][FIX] attachment_image_resize: fix not setting resize_done to true when create new attachment

[AungKoKoLin1997]

4981
Only the previous logic is not covered to set the resize_done to True since there is still no record at the time of image processing during creation.

[yostashiro]

@AungKoKoLin1997 Can you please clarify what the issue we are facing is. While I think the proposed change is probably needed, I wasn't sure it was addressing the issue.

[AungKoKoLin1997]

@AungKoKoLin1997 Can you please clarify what the issue we are facing is. While I think the proposed change is probably needed, I wasn't sure it was addressing the issue.

@yostashiro The issue we are facing now is the resize_done is never True when the attachment is created but the resizing is working well. It is because of self is still not a record in _postprocess_contents during creation.
So, resize_done is never assigned for the new creation.

[yostashiro]

@AungKoKoLin1997 In that case, shouldn't we instead update _postprocess_contents() by updating values when self is not a record? The suggested update blurs the intention without a comment.

[yostashiro]

LGTM.

[nobuQuartile]

LGTM
Functional review
Code review