feat(demo): disable features on demo env [EE-1874] (#6040)

api/http/middlewares/demo.go

@@ -0,0 +1,23 @@
+package middlewares
+
+import (
+	"net/http"
+
+	"github.com/gorilla/mux"
+	httperror "github.com/portainer/libhttp/error"
+	"github.com/portainer/portainer/api/http/errors"
+)
+
+// restrict functionality on demo environments
+func RestrictDemoEnv(isDemo func() bool) mux.MiddlewareFunc {
+	return func(next http.Handler) http.Handler {
+		return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+			if !isDemo() {
+				next.ServeHTTP(w, r)
+				return
+			}
+
+			httperror.WriteError(w, http.StatusBadRequest, errors.ErrNotAvailableInDemo.Error(), errors.ErrNotAvailableInDemo)
+		})
+	}
+}