Redirect user based on DefaultDomainRedirect for the given Pages project

What does this MR do?

Redirect user based on DefaultDomainRedirect for the given Pages project. This MR is dependent on gitlab!173510 (merged).

Related: #1131 (closed)

Changelog: added

TODO

• Feature flag
  • Added feature flag:
  • This feature does not require a feature flag
• I added the Changelog trailer to the commits that need to be included in the changelog (e.g. Changelog: added)
• I added unit tests or they are not required
• I added acceptance tests or they are not required
• I added documentation (or it's not required)
• I followed code review guidelines
• I followed Go Style guidelines

internal/defaultdomainredirect/middleware_test.go

+package defaultdomainredirect
+
+import (
+	"net/http"
+	"net/http/httptest"
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+func TestMiddlewareRedirectsToDefaultDomain(t *testing.T) {
+	finalHandler := http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		w.WriteHeader(http.StatusOK)
+	})
+
+	middleware := NewMiddleware(finalHandler)
+
+	tests := []struct {
+		name               string
+		requestHost        string
+		requestPath        string
+		defaultDomain      string
+		prefix             string
+		expectedStatusCode int
+		expectedLocation   string
+	}{
+		{
+			name:               "redirect to default domain",
+			requestHost:        "example.com",
+			requestPath:        "/path/to/resource",
+			defaultDomain:      "https://default.example.com",
+			expectedStatusCode: http.StatusPermanentRedirect,
+			expectedLocation:   "https://default.example.com/path/to/resource",
+		},
+		{
+			name:               "no redirect if already on default domain",
+			requestHost:        "default.example.com",
+			requestPath:        "/path/to/resource",
+			defaultDomain:      "https://default.example.com",
+			expectedStatusCode: http.StatusOK,
+		},
+		{
+			name:               "no redirect if defaultDomainRedirect is empty",
+			requestHost:        "example.com",
+			requestPath:        "/path/to/resource",
+			defaultDomain:      "",
+			expectedStatusCode: http.StatusOK,
+		},
+		{
+			name:               "invalid default domain",
+			requestHost:        "example.com",
+			requestPath:        "/path/to/resource",
+			defaultDomain:      "://invalid-url",
+			expectedStatusCode: http.StatusOK,
+		},
+	}
+
+	for _, tc := range tests {
+		t.Run(tc.name, func(t *testing.T) {
+			getDefaultDomainRedirectAndPrefixFunc = func(r *http.Request) (string, string) {
+				return tc.defaultDomain, ""
+			}
+
+			r := httptest.NewRequest(http.MethodGet, "http://"+tc.requestHost+tc.requestPath, nil)
+			r.Host = tc.requestHost
+
+			rec := httptest.NewRecorder()
+			middleware.ServeHTTP(rec, r)
+
+			require.Equal(t, tc.expectedStatusCode, rec.Code)
+
+			if tc.expectedStatusCode == http.StatusPermanentRedirect {
+				require.Equal(t, tc.expectedLocation, rec.Header().Get("Location"))
+			} else {
+				require.Empty(t, rec.Header().Get("Location"))
+			}
+		})
+	}
+}