add min_posts, max_posts to filter the topic list queries

superseeds #2412

lib/topic_query.rb

@@ -13,6 +13,8 @@ class TopicQuery
                      limit
                      page
                      per_page
+                     min_posts
+                     max_posts
                      topic_ids
                      visible
                      category
@@ -266,6 +268,9 @@ class TopicQuery
         end
       end
 
+      result = result.where('topics.posts_count <= ?', options[:max_posts]) if options[:max_posts].present?
+      result = result.where('topics.posts_count >= ?', options[:min_posts]) if options[:min_posts].present?
+
       guardian = Guardian.new(@user)
       if !guardian.is_admin?
         allowed_ids = guardian.allowed_category_ids