fix extend susbcription w/ payment schedule

app/models/subscription.rb

@@ -85,6 +85,12 @@ class Subscription < ApplicationRecord
     statistic_profile.user
   end
 
+  def original_payment_schedule
+    return payment_schedule if payment_schedule
+
+    PaymentScheduleItem.where("cast(details->>'subscription_id' AS int) = ?", id).first&.payment_schedule
+  end
+
   private
 
   def notify_member_subscribed_plan

app/services/subscriptions/subscribe.rb

@@ -53,7 +53,7 @@ class Subscriptions::Subscribe
       expiration_date: new_expiration_date
     )
     if new_sub.save
-      schedule = subscription.payment_schedule
+      schedule = subscription.original_payment_schedule
       details = Price.compute(true, new_sub.user, nil, [], plan_id: subscription.plan_id)
       payment = if schedule
                   generate_schedule(subscription: new_sub,

doc/postgresql_readme.md

@@ -80,3 +80,4 @@ This is currently not supported, because of some PostgreSQL specific instruction
  - `db/migrate/20200623141305_update_search_vector_of_projects.rb` defines a PL/pgSQL function (`fill_search_vector_for_project()`) and create an SQL trigger for this function;
  - `db/migrate/20200629123011_update_pg_trgm.rb` is using [ALTER EXTENSION](https://www.postgresql.org/docs/10/sql-alterextension.html);
  - `db/migrate/20201027101809_create_payment_schedule_items.rb` is using [jsonb](https://www.postgresql.org/docs/9.4/static/datatype-json.html);
+- `app/models/subscription.rb@original_payment_schedule` is using `->>` and `cast(... AS int)` for querying a with jsonb column.