Cleanup Connection headers before passing the middleware chain

Co-authored-by: Romain <rtribotte@users.noreply.github.com>

pkg/middlewares/connectionheader/connectionheader.go

@@ -1,46 +0,0 @@
-package connectionheader
-
-import (
-	"net/http"
-	"net/textproto"
-	"strings"
-
-	"golang.org/x/net/http/httpguts"
-)
-
-const (
-	connectionHeader = "Connection"
-	upgradeHeader    = "Upgrade"
-)
-
-// Remover removes hop-by-hop headers listed in the "Connection" header.
-// See RFC 7230, section 6.1.
-func Remover(next http.Handler) http.HandlerFunc {
-	return func(rw http.ResponseWriter, req *http.Request) {
-		var reqUpType string
-		if httpguts.HeaderValuesContainsToken(req.Header[connectionHeader], upgradeHeader) {
-			reqUpType = req.Header.Get(upgradeHeader)
-		}
-
-		removeConnectionHeaders(req.Header)
-
-		if reqUpType != "" {
-			req.Header.Set(connectionHeader, upgradeHeader)
-			req.Header.Set(upgradeHeader, reqUpType)
-		} else {
-			req.Header.Del(connectionHeader)
-		}
-
-		next.ServeHTTP(rw, req)
-	}
-}
-
-func removeConnectionHeaders(h http.Header) {
-	for _, f := range h[connectionHeader] {
-		for _, sf := range strings.Split(f, ",") {
-			if sf = textproto.TrimString(sf); sf != "" {
-				h.Del(sf)
-			}
-		}
-	}
-}