fix: add null menu handler, for use with API apps

tailbone/menus.py

@@ -745,3 +745,18 @@ class MenuHandler(TailboneMenuHandler):
                       "please use tailbone.menus.TailboneMenuHandler instead",
                       DeprecationWarning, stacklevel=2)
         super().__init__(*args, **kwargs)
+
+
+class NullMenuHandler(WuttaMenuHandler):
+    """
+    Null menu handler which uses an empty menu set.
+
+    .. note:
+
+       This class shouldn't even exist, but for the moment, it is
+       useful to configure non-traditional (e.g. API) web apps to use
+       this, in order to avoid most of the overhead.
+    """
+
+    def make_menus(self, request, **kwargs):
+        return []