Schema for subscriptions (master record).

Subscriptions are controlled internally by PhoenixKit, NOT by payment providers. This allows using any payment provider (even those without subscription APIs) and provides full control over subscription lifecycle.

Status Lifecycle

trialing -> active -> [past_due -> active] -> cancelled
                   -> paused -> active
                   -> cancelled

• trialing - Free trial period active
• active - Subscription is active and paid
• past_due - Payment failed, in grace period
• paused - Subscription temporarily paused by user
• cancelled - Subscription ended

Renewal Process

Renewals are handled by Oban workers:

1. SubscriptionRenewalWorker runs daily, checks subscriptions near period end
2. Creates invoice for the subscription
3. Charges saved payment method via provider
4. On success: extends current_period_end
5. On failure: sets status to past_due, increments renewal_attempts

Grace Period (Dunning)

When payment fails:

1. Status changes to past_due
2. grace_period_end is set (configurable days)
3. SubscriptionDunningWorker retries payment
4. After max attempts or grace period end: subscription cancelled