Merge branch '470551_allow_enable_member_promotion_management_via_api' into 'master'

Adds enable_member_management setting to api response

See merge request https://gitlab.com/gitlab-org/gitlab/-/merge_requests/168356



Merged-by: Vijay Hawoldar <vhawoldar@gitlab.com>
Approved-by: Surabhi Suman <ssuman@gitlab.com>
Approved-by: Vijay Hawoldar <vhawoldar@gitlab.com>
Reviewed-by: Jason Goodman <jgoodman@gitlab.com>
Reviewed-by: Vijay Hawoldar <vhawoldar@gitlab.com>
Reviewed-by: Sheldon Led <sheldonled@gitlab.com>
Reviewed-by: Surabhi Suman <ssuman@gitlab.com>
Co-authored-by: Sheldon Led <sheldonled@gitlab.com>
Co-authored-by: Sheldon Led <sheldonled@gmail.com>
Co-authored-by: Suraj Tripathi <stripathi@gitlab.com>