Nginx is not resolving SSIs in application/octet-stream type files from a server

Question

I have create a new stack where Nginx server act as a reverse proxy between a CDN server and the browser, and the Nginx server supposed to resolve SSIs of all the HTML files from the CDN. The issue is Nginx server resolves only Content-type:text/html type files not application/octet-stream (even though all of them are actual .html files despite the content-type, it is a glitch on our company's CDN)

    location /path/ {
        ssi on;
        add_header Content-Type text/html;
        proxy_pass https://example-cdn.com/path/;
    }

Is there a way to force Nginx to resolve any file as long as the extension is .html despite the Content-type header in the CDN response?

Answer 1

I created a secondary server in the same config, rewriting the Content-Type based on the extension and consuming the content for the primary nginx server from there.

Secondary server in the same config

# Mapping
map $uri $custom_content_type {
    default "application/octet-stream";
    ~(.*.json)$ "application/json";
    ~(.*.html)$ "text/html";
    ~(.*.pdf)$ "application/pdf";
}

server {
    listen       8090;
    server_name  localhost;

    location /path/ {
        proxy_hide_header Content-Type;
        add_header Content-Type $custom_content_type;
        proxy_pass https://example-cdn.com/path/;
    }
}   

Primary server

location /path/ { 
    proxy_pass http://localhost:8090/path/;
}

still open for a more efficient solution.