It persist temporary personal snippets under
user/:id namespaces temporarily while creating
a upload record to track it. If an user gets removed
while it's still a tmp upload, it also gets removed.
If the tmp upload is sent, the upload gets moved to
personal_snippets/:id as before. The upload record
also gets updated to the new model type as well.
When object storage is enabled, the logos used to customize a GitLab
appearance causes the time-limited URLs to be used. We fix this
by forcing all of these URLs to use the /uploads/-/system prefix
so that they will always be proxied through GitLab.
Closes https://gitlab.com/gitlab-org/gitlab-ee/issues/6778
