Add ability to use nested only parameter

- The only string works much the same as before with its comma separation
-- Nested includes are indicated with square brackets "[ ]"
-- The nested include is the value immediately preceding the square brackets
-- The only string is the comma separated string inside those brackets
- Default includes are split between format types when necessary
-- This prevents unnecessary includes from being added on page load
- Available includes are those items which are allowed to be accessible to the user
-- Some aren't because they are sensitive, such as the creator of a flag
-- Some aren't because the number of associated items is too large
- The amount of times the same model can be included to prevent recursions
-- One exception is the root model may include the same model once
--- e.g. the user model can include the inviter which is also the user model
-- Another exception is if the include is a has_many association
--- e.g. artist urls can include the artist, and then artist urls again

app/controllers/forum_topics_controller.rb

@@ -23,10 +23,7 @@ class ForumTopicsController < ApplicationController
     params[:search][:order] ||= "sticky" if request.format == Mime::Type.lookup("text/html")
     params[:limit] ||= 40
 
-    @forum_topics = ForumTopic.paginated_search(params)
-
-    @forum_topics = @forum_topics.includes(:creator, :updater, :forum_topic_visit_by_current_user).load if request.format.html?
-    @forum_topics = @forum_topics.includes(:creator, :original_post).load if request.format.atom?
+    @forum_topics = ForumTopic.paginated_search(params).includes(model_includes(params))
 
     respond_with(@forum_topics)
   end
@@ -80,6 +77,16 @@ class ForumTopicsController < ApplicationController
 
   private
 
+  def default_includes(params)
+    if ["json", "xml"].include?(params[:format])
+      []
+    elsif params[:format] == "atom"
+      [:creator, :original_post]
+    else
+      [:creator, :updater, :forum_topic_visit_by_current_user]
+    end
+  end
+
   def normalize_search
     if params[:title_matches]
       params[:search] ||= {}