oobmigration: derive subscription account number and extract license key fields
Created by: unknwon
This PR adds two OOB migrations:
- Attempt to extract the account number from the associated user of subscriptions, sister PR: https://github.com/sourcegraph/sourcegraph/pull/39209
- Extract license fields from the license key text and store them to dedicated columns, sister PR: https://github.com/sourcegraph/sourcegraph/pull/39215
Test plan
Manually e2e tested locally.
Part of https://github.com/sourcegraph/sourcegraph/issues/38661