A DeployToken responds to `:username`, but it returns the username for the
token, not a User object. Don't attempt to log user activity in this case.
Closesgitlab-org/gitlab-ee#7080
In GitLab EE, a GitLab instance can be read-only (e.g. when it's a Geo
secondary node). But in GitLab CE it also might be useful to have the
"read-only" idea around. So port it back to GitLab CE.
Also having the principle of read-only in GitLab CE would hopefully
lead to less errors introduced, doing write operations when there
aren't allowed for read-only calls.
Closesgitlab-org/gitlab-ce#37534.
