Remove Cloudflare and X-Forwarded-* headers in piped-proxy

[ornate-lemon-horse]

Currently, when set up using the AIO docker config, the CF-Connecting-IP and X-Forwarded-For headers are removed by both nginx [1] and Caddy [2] (I was unable to to determine if this is done for Kubernetes as well) for requests it sends to piped-proxy. However, this protection is incomplete:

1. There is a list of additional CF-* headers as well as X-Forwarded-Proto, True-Client-IP and CDN-Loop in Cloudflare's documentation [3] that can identify the request as not coming directly from a client device.
2. The default behavior for both Caddy [4] and nginx [5] is for all headers to be passed when proxying the request, with some exceptions, and the AIO docker config does not turn these off. (I am not familiar with Kubernetes so I can't tell if the provided config is doing the same)
3. Caddy itself will set X-Forwarded-Proto and X-Forwarded-Host along with X-Forwarded-For when it proxies the request [4] unless those headers are manually removed.
4. It doesn't appear like any configs are doing this currently, but the Forwarded header will contain the same information as the X-Forwarded-* ones if it is added by whatever load balancer/reverse proxy is in use.

Based on this, I'm thinking if it might be better to strip these headers in piped-proxy instead of relying on the Docker AIO config or custom load balancer solution to do it.

The current list at the time of this writing seems to be:

• CF-Connecting-IP
• CF-Connecting-IPv6
• CF-EW-Via
• CF-Pseudo-IPv4
• True-Client-IP
• CF-RAY
• CF-IPCountry
• CF-Visitor
• CDN-Loop
• CF-Worker
• X-Forwarded-For
• X-Forwarded-Proto
• X-Forwarded-Host

[1] https://github.com/TeamPiped/Piped-Docker/blob/main/template/ytproxy.conf#L3
[2] https://github.com/TeamPiped/Piped-Docker/blob/main/template/Caddyfile#L41
[3] https://developers.cloudflare.com/fundamentals/reference/http-request-headers/
[4] https://caddyserver.com/docs/caddyfile/directives/reverse_proxy#defaults
[5] https://nginx.org/en/docs/http/ngx_http_proxy_module.html#proxy_pass_request_headers and note the default setting is on