nginx auth proxy

https://github.com/nginxinc/nginx-ldap-auth
https://github.com/kvspb/nginx-auth-ldap
https://serverfault.com/questions/844205/add-ldap-authentication-to-nginx-on-rhel-7
https://gist.github.com/pyle/cdc7d7c2ac9dfecfff6e892fd0195eaf
https://github.com/cogolabs/transcend