Discourse automatically sends a private message after backup or
restore finished. The private message used to contain the log inline
even when it was very long. A very long log can create issues because
the length of the post will be over the maximum allowed length of a
post. When that happens, Discourse will try to create an upload with
the logs. If that fails, it will trim the log and inline it.
Follow up to [FIX: Empty backup names with unicode site titles][1]
- Use .presence - "It's cleaner"
- Update spec to use System.system_user so it is more readable
[1]: c8661674d4
