schedule-effective-dated-changeslisted

# Schedule effective-dated changes Applying a change at a **future effective date** (plan/tier/price changes, scheduled deactivations, end-of-billing-cycle updates) without mutating now. The Redis *delayed job* alternative (and the cron + overlap lock) is `background-jobs-and-caching`; transactions are `write-service-code` §9. ## Core principle **Persist the *intended change* as a row with an effective date — don't mutate now, and don't bury the timer in memory.** A pending-changes table makes a future change **queryable** ("what's scheduled?"), **cancellable** (the user changes their mind), and **auditable** (history of what applied when). A scheduled sweep applies the **due** ones transactionally and records history. ## 1. Store the intent, not the mutation A `pending_changes` table holds the change payload + when it takes effect + its lifecycle status — instead of writing the change to the live row immediately: ```ts @Entity() class PendingChange extends BaseEntity { @Column() targetId!: string; // the entity to change @Column({ type: 'jsonb' }) data!: ChangePayload; // WHAT changes (new tier, new price, …) @Column() effectiveAt!: Date; // WHEN it takes effect @Column({ type: 'enum', enum: PendingStatus, default: PendingStatus.PENDING }) status!: PendingStatus; @Column({ nullable: true }) reason!: Nullable<string>; // why it FAILED / was CANCELLED } // PENDING → COMPLETED | FAILED | CANCELLED ``` Now "show my scheduled change