FIX: local post onebox was always pointing to 1st post

lib/onebox/templates/discourse_topic_onebox.hbs

@@ -1,4 +1,4 @@
-<aside class='quote' data-post="1" data-topic="{{topic_id}}">
+<aside class='quote' data-post="{{post_number}}" data-topic="{{topic_id}}">
   <div class='title'>
     <div class='quote-controls'></div>
     {{{avatar}}}

lib/oneboxer.rb

@@ -202,6 +202,7 @@ module Oneboxer
       else
         args = {
           topic_id: topic.id,
+          post_number: post.post_number,
           avatar: PrettyText.avatar_img(post.user.avatar_template, "tiny"),
           original_url: url,
           title: PrettyText.unescape_emoji(CGI::escapeHTML(topic.title)),

spec/components/oneboxer_spec.rb

@@ -54,6 +54,7 @@ describe Oneboxer do
 
       onebox = preview(public_reply.url, user, public_category)
       expect(onebox).to include(public_reply.excerpt)
+      expect(onebox).to include(%{data-post="2"})
       expect(onebox).to include(PrettyText.avatar_img(replier.avatar_template, "tiny"))
 
       onebox = preview(public_reply.url, user, public_category, public_topic)