ProxyController.cs

    public class ProxyController : ApiController
    {

        [HttpGet, HttpPost]
        [Route("proxy/call")]
        public async Task<HttpResponseMessage> ProxyCall(string uri)
        {
            var queryString = "";            

            var requestQuery = Request.GetQueryNameValuePairs();
            var qparams = requestQuery as KeyValuePair<string, string>[] ?? requestQuery.ToArray();
            for (int i = 1; i <= qparams.Count() - 1; i++)
            {
                if (string.IsNullOrEmpty(qparams[i].Key))
                    continue;

                var key = HttpUtility.UrlEncode(qparams[i].Key);
                var value = HttpUtility.UrlEncode(qparams[i].Value);

                queryString += ((i == 1) ? "?" : "&") + $"{key}={value}";
            }

            var requestUri = new Uri(uri);            

            requestUri = new Uri(requestUri.AbsoluteUri + queryString);

            using (var handler = new WebRequestHandler())
            {
                handler.ServerCertificateValidationCallback += (sender, cert, chain, sslPolicyErrors) => true;

                HttpResponseMessage response;

                Request.RequestUri = requestUri;

                if (Request.Method != HttpMethod.Post)
                {
                    Request.Content = null;
                }

                using (HttpClient client = new HttpClient(handler))
                {
                    response = await client.SendAsync(Request, HttpCompletionOption.ResponseContentRead);
                }
                
                return response;
            }
        }
    }

Toying around with a basic forwarder to supplement Lead Forensics tracking call which does not support embedding into HTTPS sites.

Example usage for the Lead Forensics Js call to the HTTP tracker endpoint from my HTTPS enabled site:
var link = document.location.href + '/proxy/call?uri=http://www.66-trk-srv.com/Track/Capture.aspx&retType=js&