docker-nginx.conf

# In Dockerfile, this will replace /etc/nginx/conf.d/default.conf
server {
    listen 80;
    listen [::]:80;
    server_name localhost;

    # Ensure that Nginx will not rewrite the double slashes in `https://`, like in:
    #   /proxy/https://example.com/a/b/c
    # ...to become a single slash:
    #   /proxy/https:/example.com/a/b/c
    # In `proxy_pass` below, the above would eventually throw:
    #   invalid URL prefix in "https:/example.com/a/b/c"
    # Note that, when specified in `server`, this only works for the default server;
    # see https://nginx.org/en/docs/http/ngx_http_core_module.html#merge_slashes
    merge_slashes off;

    location / {
        root /usr/share/nginx/html;
        # Forward all non-existing paths, such as /configuration and /search, to the app
        try_files $uri $uri/ /index.html;
    }

    location ~ /proxy/(?<target>.+) {
        # Proxy requests for:
        #   /proxy/https://example.com/a/b/c
        # ...to:
        #   https://example.com/a/b/c
        proxy_pass $target;

        # When not using a static target, a resolver is needed, for otherwise Nginx throws:
        #   no resolver defined to resolve <target name>
        # Use Cloudflare DNS; https://www.cloudflare.com/learning/dns/what-is-1.1.1.1/
        resolver 1.1.1.1;
    }

    # Redirect server error pages to the static page /50x.html
    error_page 500 502 503 504  /50x.html;
    location = /50x.html {
        root /usr/share/nginx/html;
    }
}