FEATURE: Shared Drafts

This feature can be enabled by choosing a destination for the
`shared drafts category` site setting.

* Staff members can create shared drafts, choosing a destination
category for the topic when it is published.

* Shared Drafts can be viewed in their category, or above the
topic list for the destination category where it will end up.

* When the shared draft is ready, it can be published to the
appropriate category by clicking a button on the topic view.

* When published, Drafts change their timestamps to the current
time, and any edits to the original post are removed.

lib/topic_creator.rb

@@ -48,12 +48,18 @@ class TopicCreator
     save_topic(topic)
     create_warning(topic)
     watch_topic(topic)
+    create_shared_draft(topic)
 
     topic
   end
 
   private
 
+  def create_shared_draft(topic)
+    return unless @opts[:shared_draft] && @opts[:category].present?
+    SharedDraft.create(topic_id: topic.id, category_id: @opts[:category])
+  end
+
   def create_warning(topic)
     return unless @opts[:is_warning]
 
@@ -138,6 +144,10 @@ class TopicCreator
     # PM can't have a category
     @opts.delete(:category) if @opts[:archetype].present? && @opts[:archetype] == Archetype.private_message
 
+    if @opts[:shared_draft]
+      return Category.find(SiteSetting.shared_drafts_category)
+    end
+
     # Temporary fix to allow older clients to create topics.
     # When all clients are updated the category variable should
     # be set directly to the contents of the if statement.