Add message threads #394

This new view sorts the messages by threads based on the reply_to.
Now we store only the message which started a new thread in the reply_to
field to avoid recursive queries.

plugins/messages/app/controllers/message_threads_controller.rb

@@ -0,0 +1,12 @@
+class MessageThreadsController < ApplicationController
+
+  before_filter -> { require_plugin_enabled FoodsoftMessages }
+
+  def index
+    @message_threads = Message.pub.threads.page(params[:page]).per(@per_page).order(created_at: :desc).includes(:sender)
+  end
+
+  def show
+    @messages = Message.thread(params[:id]).order(:created_at)
+  end
+end