Issue Onebox in HTTPS

Which headers would that be?

Here’s what I have:

location / {
            proxy_pass http://unix:/var/discourse/shared/standalone/nginx.http.sock;
            proxy_set_header Host $http_host;                                                                                                     
            proxy_http_version 1.1;
            proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
            proxy_set_header X-Forwarded-Proto $scheme;                                                                                           
            client_max_body_size 20M;
            error_page 502 =502 /errorpages/offline.html;
            proxy_intercept_errors on;
            error_page 500 503 504 /errorpages/50x.html;
}