nginx-proxy-manager/docker/rootfs/etc/nginx/conf.d/include/proxy.conf

add_header       X-Served-By $host;
proxy_set_header Host $host;
proxy_set_header X-Forwarded-Scheme $scheme;
proxy_set_header X-Forwarded-Proto  $scheme;
proxy_set_header X-Forwarded-For    $proxy_add_x_forwarded_for;
proxy_set_header X-Real-IP          $remote_addr;
proxy_pass       $forward_scheme://$server:$port$request_uri;