- Original EE MR: https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/14827

Regenerate discussion_id for notes that are being copied over to the
epic when issue is promoted to epic.

https://gitlab.com/gitlab-org/gitlab-ee/issues/11445

This is a port MR for CE

Original MR:

https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/14141

Adds system notes for labels, milestone and due date on create

Extract code to make it easier reusable
- introduce AttributesRewriter and ContentRewriter
  - support group entites when rewriting content
- make Uploader copy_to working for Namespaces

This whitelists all existing offenses for the various CodeReuse cops, of
which most are triggered by the CodeReuse/ActiveRecord cop.

For directories application_settings --> labels.

Partially addresses #47424.

The merge request counter in the UI was not decreasing when a merge
request was deleting.

This was just due to the cache not being
refreshed on a delete action.

fixes: https://gitlab.com/gitlab-org/gitlab-ce/issues/44458

When the target is deleted, todos are destroyed, but we did not reset the todo
cache for users with todos on the deleted target. This would only update after
the next time the todo cache was updated for that user.

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>