rocket-nginx: Pre-Set nginx Headers are ignored/unset for cached pages

Describe the bug Well described here: https://www.peterbe.com/plog/be-very-careful-with-your-add_header-in-nginx

If you add any global nginx headers with add_header they are discarded by

# Add header to HTML cached files
location ~ /wp-content/cache/wp-rocket/.*html$ {
        etag on;
        add_header Vary "Accept-Encoding, Cookie";
        ....
}

# Do not gzip cached files that are already gzipped
location ~ /wp-content/cache/wp-rocket/.*_gzip$ {
        etag on;
        gzip off;
        types {}
        default_type text/html;
        add_header Content-Encoding gzip;
        ....
}

Versions What version of Nginx are you using ? 1.16.1

What version of Rocket-Nginx are you using ? origin/master (2.1.1)

What version of WP Rocket are you using ? 3.3.7

Are you using Nginx as a reverse proxy (with Apache for instance) ? No

To Reproduce Steps to reproduce the behaviour: Add any header to you vhost config before you add include /etc/nginx/rocket-nginx/default.conf; like:

server {
        ....
        add_header X-XSS-Protection "1; mode=block";
        add_header X-Content-Type-Options "nosniff";
        include /etc/nginx/rocket-nginx/default.conf;
       ....
}

1. Call a page that is not cached: You will see the headers from the server block + the rocket-nginx headers that are NOT in the location block.

2. Call a cached page and you will see that they are missing.

Did you activate the debug in Rocket-Nginx ? Please do and include any headers. not necessary

Expected behavior The previously set global headers should remain set for cached pages. Thus no add_header must be called within rocket-nginx location blocks for cached pages. Outside of the location blocks should work fine.

Additional context Add any other context about the problem here.