feat: add subscription billing foundation (schema, types, repository)

[Ferryx349]

Description

Groundwork for subscription-based relay billing. Adds database schema, TypeScript types, settings shape, and repository layer only, no enforcement, workers, or payment flow changes. One-time admission billing remains unchanged.
Follows the same pattern as NIP-43 invite codes (#650): migration + types + repository + tests, nothing wired into runtime behavior yet.

Changes

Database

• New user_subscriptions table (pubkey PK, stable id UUID for invoice FK)
  • plan_id, status, period timestamps, grace_until, cancel_at_period_end
  • Index on (status, current_period_end) for future worker queries
• Extended invoices with nullable columns:
  • fee_schedule (admission | subscription | publication, default admission)
  • plan_id, subscription_id, period_start, period_end
    Plans live in settings (payments.subscriptionPlans[]), not a DB table.

Related Issue

Part of :- #673

Motivation and Context

How Has This Been Tested?

Screenshots (if appropriate):

Types of changes

• Non-functional change (docs, style, minor refactor)
• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my code changes.
• I added a changeset, or this is docs-only and I added an empty changeset.
• All new and existing tests passed.

[changeset-bot]

🦋 Changeset detected

Latest commit: 2452287

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
nostream	Minor

Not sure what this means? Click here to learn what changesets are.

Click here if you're a maintainer who wants to add another changeset to this PR

[Copilot]

Pull request overview

Adds the initial data-layer foundation for subscription-based relay billing (schema, settings/types, and repositories) without wiring any runtime enforcement or payment flow changes, aligning with the prior “foundation-only” pattern used for invite codes.

Changes:

• Introduces user_subscriptions persistence + repository methods for lookup/upsert and future renewal/expiry queries.
• Extends invoices with subscription billing fields (fee_schedule, plan_id, subscription_id, period_start/end) and updates invoice mapping/upsert behavior plus tests.
• Adds settings/types/docs support for payments.subscriptionPlans[] and a changeset for the feature flag groundwork.

Reviewed changes

Copilot reviewed 13 out of 13 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
test/unit/repositories/user-subscription-repository.spec.ts	Adds unit coverage for the new subscription repository behaviors.
test/unit/repositories/invoice-repository.spec.ts	Extends invoice repository tests for new subscription-related columns and defaults.
src/utils/transform.ts	Maps new invoice DB columns onto the Invoice domain type.
src/repositories/user-subscription-repository.ts	New repository implementing subscription CRUD/query primitives.
src/repositories/invoice-repository.ts	Adds fee_schedule defaulting and includes new subscription columns in invoice upsert row shape.
src/@types/user-subscription.ts	Introduces subscription domain/DB row types and SubscriptionStatus enum.
src/@types/settings.ts	Adds subscription plan type definitions to settings schema.
src/@types/repositories.ts	Exposes IUserSubscriptionRepository interface.
src/@types/invoice.ts	Adds InvoiceFeeSchedule and optional subscription invoice fields.
resources/default-settings.yaml	Adds payments.subscriptionPlans default; removes an admin TTL entry (see comment).
migrations/20260708_120000_create_subscription_billing_foundation.js	Creates user_subscriptions, adds indexes/FKs, and extends invoices with subscription columns.
CONFIGURATION.md	Documents the new payments.subscriptionPlans[] settings surface.
.changeset/subscription-billing-foundation.md	Declares a minor release changeset for the new foundation.

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.

[coveralls]

coverage: 67.762% (+0.02%) from 67.747% — Ferryx349:Billing into cameri:main