Do not expose server details

[Maciej Brencz]

Inspired by https://github.com/bunkerity/bunkerized-nginx

https://serverfault.com/a/1015876/448086

server_tokens "";

fails with: #26 1.388 nginx: [emerg] invalid value "" in /etc/nginx/nginx.conf:35

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or

https://github.com/openresty/headers-more-nginx-module#more_clear_headers:

 more_clear_headers 'server';

Installation instructions // more headers

https://github.com/bunkerity/bunkerized-nginx/blob/master/helpers/install.sh#L491-L493

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And https://www.upguard.com/blog/10-tips-for-securing-your-nginx-deployment

• Disable TRACE and TRACK.
• Configure Nginx to Include an X-Frame-Options Header.
• Modify Nginx Web Server Configuration/SSL for X-XSS protection