feat: user_ips の id を削除（#231） (#238)

#231

Co-authored-by: miteruzo <miteruzo@naver.com>
Reviewed-on: #238

backend/app/models/user_ip.rb

@@ -1,4 +1,6 @@
 class UserIp < ApplicationRecord
+  self.primary_key = :user_id, :ip_address_id
+
   belongs_to :user
   belongs_to :ip_address