collab: Add `external_id` column to `billing_customers` table (#42923)

This PR adds an `external_id` column to the `billing_customers` table.

Release Notes:

- N/A
73d3f9611eMarshall Bowers committed on 11/17/2025, 10:12:00 PM· committed by GitHubparentd9cfc2c
1 file changedLine totals unavailable