Update changelog with Customer Portal improvements and cancellation metrics

[Copilot]

Updates the changelog to reflect recent changes since 2025-09-13 with a new entry dated 2025-09-22 containing two key improvements:

Customer Portal Invoice Preview Enhancement

Merged and rephrased improvements from PRs #6908 ("Update 'Current Period Overview' after subscription changes") and #6867 ("Add endpoint to preview upcoming subscription charge including taxes") into a single user-facing changelog entry. The combined feature enhances the Customer Portal to provide clearer and more accurate invoice previews that update automatically after subscription changes and include all relevant taxes.

Cancellation Metrics

Added a new changelog entry for detailed cancellation metrics (PR #6900) that provides clearer insights into subscription cancellations and their business impact.

Both entries include proper PR references and author attribution as specified. No existing customer balance entries were found that required removal, consistent with the internal-only nature of that feature.

The changelog formatting follows the established MDX structure and maintains consistency with existing entries.

This pull request was created as a result of the following prompt from Copilot chat.

Update the changelog to reflect recent changes since 2025-09-13:

• Remove mention of "Add customer balance" (internal only, not user-facing)
• Merge and rephrase:
  • Update "Current Period Overview" after subscription changes #6908 ("Update 'Current Period Overview' after subscription changes")
  • Add endpoint to preview upcoming subscription charge including taxes #6867 ("Add endpoint to preview upcoming subscription charge including taxes")
    as a single point: "Improve preview of next invoice in Customer Portal"
• Add a new changelog entry dated today (2025-09-22) in docs/changelog/recent.mdx with the following points:

---

Improve preview of next invoice in Customer Portal

We've enhanced the Customer Portal to provide a clearer and more accurate preview of your next invoice. The overview now updates automatically after subscription changes, and you can preview upcoming charges with all relevant taxes included.

---

Cancellation metrics

We've added detailed cancellation metrics, giving you clearer insights into subscription cancellations and their impact on your business performance.

---

Each entry should reference the appropriate pull requests and authors:

• "Improve preview of next invoice in Customer Portal" (#6908, #6867) — by pieterbeulque
• "Cancellation metrics" (#6900) — by pieterbeulque

Do not include the customer balance point (#6742), as it is internal.

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2 Skipped Deployments

Project	Deployment	Preview	Comments	Updated (UTC)
polar	Ignored	Preview		Sep 22, 2025 5:17pm
polar-sandbox	Ignored	Preview		Sep 22, 2025 5:17pm

[github-actions]

Images automagically compressed by Calibre's image-actions ✨

Compression reduced images by 90.1%, saving 1,016.8 KB.

Filename	Before	After	Improvement	Visual comparison
docs/assets/changelog/2025-09-22/cancellation-metrics-example.png	1.1 MB	111.4 KB	90.1%	View diff