I added:
proxy_set_header X-Forwarded-Ssl on;
I think if nginx is used as main back-end (without Apache), this header
means nothing.
In this case just refer this guide:
https://scotthelme.co.uk/setting-up-hsts-in-nginx/
If I'm not right, and there is also Apache server, follow:
http://stackoverflow.com/questions/16042647/whats-the-de-facto-standard-for…
С наилучшими пожеланиями,
Яницкий Вадим.