FEATURE: Allow truncated group posts to be expanded

app/serializers/group_post_serializer.rb

@@ -1,10 +1,15 @@
+require_relative 'post_item_excerpt'
+
 class GroupPostSerializer < ApplicationSerializer
+  include PostItemExcerpt
+
   attributes :id,
-             :excerpt,
              :created_at,
              :title,
              :url,
-             :category
+             :category,
+             :post_number,
+             :topic_id
 
   has_one :user, serializer: GroupPostUserSerializer, embed: :object
   has_one :topic, serializer: BasicTopicSerializer, embed: :object