GET /contacts/by_kshema_id responds with 404 if contact not found
[#70971930] except was not working ok.
[#70971930]improve select -> mode convertion
Merge 70971930-attributes-bug to master

[Completes #70971930]
[#70592222]last_seen_at as LUA
Merge 70592222-last_seen_at to master

[Completes #70592222]
[#70592222] Add last_seen_at to ContactSerializer
Configurations for staging deploy on heroku