Cleanup Connection headers before passing the middleware chain

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

pkg/middlewares/auth/connectionheader_test.go

@@ -0,0 +1,70 @@
+package auth
+
+import (
+	"net/http"
+	"net/http/httptest"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestRemover(t *testing.T) {
+	testCases := []struct {
+		desc       string
+		reqHeaders map[string]string
+		expected   http.Header
+	}{
+		{
+			desc: "simple remove",
+			reqHeaders: map[string]string{
+				"Foo":            "bar",
+				connectionHeader: "foo",
+			},
+			expected: http.Header{},
+		},
+		{
+			desc: "remove and Upgrade",
+			reqHeaders: map[string]string{
+				upgradeHeader:    "test",
+				"Foo":            "bar",
+				connectionHeader: "Upgrade,foo",
+			},
+			expected: http.Header{
+				upgradeHeader:    []string{"test"},
+				connectionHeader: []string{"Upgrade"},
+			},
+		},
+		{
+			desc: "no remove",
+			reqHeaders: map[string]string{
+				"Foo":            "bar",
+				connectionHeader: "fii",
+			},
+			expected: http.Header{
+				"Foo": []string{"bar"},
+			},
+		},
+	}
+
+	for _, test := range testCases {
+		t.Run(test.desc, func(t *testing.T) {
+			t.Parallel()
+
+			next := http.HandlerFunc(func(rw http.ResponseWriter, req *http.Request) {})
+
+			h := Remover(next)
+
+			req := httptest.NewRequest(http.MethodGet, "https://localhost", nil)
+
+			for k, v := range test.reqHeaders {
+				req.Header.Set(k, v)
+			}
+
+			rw := httptest.NewRecorder()
+
+			h.ServeHTTP(rw, req)
+
+			assert.Equal(t, test.expected, req.Header)
+		})
+	}
+}