fix(backend): Allow null for period_end in billing subscription item webhook

[jacekradko]

Description

Updates period_end to allow null in BillingSubscriptionItemWebhookEventJSON.

Previously, the API returned a negative timestamp for subscription items on the free plan. Now it returns null instead, which is a cleaner representation.

This aligns the webhook event type with the existing BillingSubscriptionItemJSON type which already allows null.

Checklist

• pnpm build passes
• Type is consistent with other period_end definitions in the codebase

References

Fixes: USER-4434

Summary by CodeRabbit

• Bug Fixes
  • Updated billing webhook event structure to properly allow null values for period end dates, ensuring more accurate handling of billing subscription data.

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Project	Deployment	Review	Updated (UTC)
clerk-js-sandbox	Ready	Preview, Comment	Jan 29, 2026 3:59pm

[changeset-bot]

🦋 Changeset detected

Latest commit: 610c3cd

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

This PR includes changesets to release 10 packages

Name	Type
@clerk/backend	Patch
@clerk/agent-toolkit	Patch
@clerk/astro	Patch
@clerk/express	Patch
@clerk/fastify	Patch
@clerk/nextjs	Patch
@clerk/nuxt	Patch
@clerk/react-router	Patch
@clerk/tanstack-react-start	Patch
@clerk/testing	Patch

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

[coderabbitai]

📝 Walkthrough

Walkthrough

This pull request updates the BillingSubscriptionItemWebhookEventJSON interface in the backend package to modify the period_end field behavior. Previously, period_end was an optional field that accepted number values. It is now a required field that accepts either a number or null. This change ensures the field is always present in webhook events while allowing null as an explicit value instead of undefined.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Linked Issues check	✅ Passed	The pull request directly addresses USER-4434 by updating the period_end field to allow null instead of returning negative timestamps.
Out of Scope Changes check	✅ Passed	All changes are scoped to the stated objective: updating period_end in BillingSubscriptionItemWebhookEventJSON and adding the changeset file.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Title check	✅ Passed	The pull request title accurately summarizes the main change: allowing null values for the period_end field in billing subscription item webhooks, which is the core modification shown in the changeset.

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commit: 610c3cd