change it so all topics MUST include a category, we store a special uncategorized category to compensate

this cleans up a bunch of internals and removes some settings

app/serializers/category_detailed_serializer.rb

@@ -23,7 +23,7 @@ class CategoryDetailedSerializer < BasicCategorySerializer
   end
 
   def is_uncategorized
-    name == SiteSetting.uncategorized_name
+    object.id == SiteSetting.uncategorized_category_id
   end
 
   def include_is_uncategorized?

app/serializers/site_serializer.rb

@@ -3,8 +3,8 @@ class SiteSerializer < ApplicationSerializer
   attributes :default_archetype,
              :notification_types,
              :post_types,
-             :uncategorized_slug,
-             :group_names
+             :group_names,
+             :uncategorized_category_id # this is hidden so putting it here
 
 
   has_many :categories, serializer: BasicCategorySerializer, embed: :objects
@@ -21,8 +21,8 @@ class SiteSerializer < ApplicationSerializer
     Post.types
   end
 
-  def uncategorized_slug
-    Slug.for(SiteSetting.uncategorized_name)
+  def uncategorized_category_id
+    SiteSetting.uncategorized_category_id
   end
 
 end