Set proxy_ssl_trusted_certificate.

Use the CA certificate bundle. For proxying secure services (like using
Vouch).

conf.d/global.conf

@@ -4,4 +4,5 @@ gzip            on;
 tcp_nopush                      on;
 tcp_nodelay                     on;
 server_tokens                   off;
+proxy_ssl_trusted_certificate   /etc/ssl/certs/ca-certificates.crt;
 include                         snippets/common-headers.conf;