I want to implement subscription functionality. I first create a subscription plan using v1/billing/plans and obtain a plan_id. Each time a user places an order, I create a subscription using https://api-m.paypal.com/v1/billing/subscriptions, obtain a subscriptions_id, store it in the database for later retrieval to mark which user is a member of which order, and return a link with ref=approve to execute the subscription payment successfully. My webhook does not seem to have a callback event for 'Payment sale completed.' Currently, I can only mark the subscription as paid and extend the user's membership by using BILLING.SUBSCRIPTION.ACTIVATED. How can I correctly monitor subscriptions? Do I need to call https://api-m.paypal.com/v1/billing/subscriptions/{id}/capture? If so, at what point should I call it?
