Add impersonation_enabled configuration
Summary
This is an upstream setting added in 11.6,
https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/23338 gitlab-org/omnibus-gitlab!2880 (merged)
This is an upstream setting added in 11.6,
https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/23338 gitlab-org/omnibus-gitlab!2880 (merged)