Add customizable user roles (#18641)

* Add customizable user roles

* Various fixes and improvements

* Add migration for old settings and fix tootctl role management

lib/simple_navigation/item_extensions.rb

@@ -0,0 +1,15 @@
+# frozen_string_literal: true
+
+module SimpleNavigation
+  module ItemExtensions
+    def url
+      if @url.nil? && @sub_navigation
+        @sub_navigation.items.first.url
+      else
+        @url
+      end
+    end
+  end
+end
+
+SimpleNavigation::Item.prepend(SimpleNavigation::ItemExtensions)