feat: add last_activity_at fallack on conv model directly

app/models/conversation.rb

@@ -124,6 +124,10 @@ class Conversation < ApplicationRecord
     last_message_in_messaging_window?(messaging_window)
   end
 
+  def last_activity_at
+    self[:last_activity_at] || created_at
+  end
+
   def last_incoming_message
     messages&.incoming&.last
   end

app/presenters/conversations/event_data_presenter.rb

@@ -40,7 +40,7 @@ class Conversations::EventDataPresenter < SimpleDelegator
     {
       agent_last_seen_at: agent_last_seen_at.to_i,
       contact_last_seen_at: contact_last_seen_at.to_i,
-      last_activity_at: last_activity_at ? last_activity_at.to_i : created_at.to_i,
+      last_activity_at: last_activity_at.to_i,
       timestamp: last_activity_at.to_i,
       created_at: created_at.to_i
     }