FIX: Old notifications didn't link to correct post after moving post

spec/fabricators/notification_fabricator.rb

@@ -5,6 +5,7 @@ Fabricator(:notification) do
   notification_type Notification.types[:mentioned]
   user
   topic { |attrs| attrs[:post]&.topic || Fabricate(:topic, user: attrs[:user]) }
+  post_number { |attrs| attrs[:post]&.post_number }
   data '{"poison":"ivy","killer":"croc"}'
 end
 
@@ -57,3 +58,17 @@ Fabricator(:posted_notification, from: :notification) do
     }.to_json
   end
 end
+
+Fabricator(:mentioned_notification, from: :notification) do
+  notification_type Notification.types[:mentioned]
+  data do |attrs|
+    {
+      topic_title: attrs[:topic].title,
+      original_post_id: attrs[:post].id,
+      original_post_type: attrs[:post].post_type,
+      original_username: attrs[:post].user.username,
+      revision_number: nil,
+      display_username: attrs[:post].user.username
+    }.to_json
+  end
+end