Let's assume that an HTTP server (which hosts the endpoint for some REST API, say) is configured to allow connections only from a single client (let's call it 1st client), i.e. from a single client IP address. If that client would run an HTTP proxy such as
squid and if another client (let's call it 2nd client) would connect through that proxy e.g. like so
<2nd-client>$ curl -x <1st-client> --cacart <cert> https://server
would the HTTP server then see the 1st or 2nd client's IP address as where the HTTP(S) request originated from? In other words, could other clients circumvent the access restricion imposed on client IP addresses by going through that proxy?