add target user to private message detail api

app/controllers/users/private_message_details_controller.rb

@@ -3,6 +3,8 @@ class Users::PrivateMessageDetailsController < Users::BaseController
 
   after_action :update_message_status, only: [:show]
 
+  helper_method :target_user
+
   def show
     messages = observed_user.private_messages.without_deleted.where(target: target_user)
 

app/views/users/private_message_details/show.json.jbuilder

@@ -1,4 +1,7 @@
 json.count @count
+json.target do
+  json.partial! 'users/user_simple', user: target_user
+end
 json.messages do
   json.array! @messages.each do |message|
     json.extract! message, :id, :user_id, :receiver_id, :sender_id, :content