Solves https://github.com/twentyhq/private-issues/issues/253
**TLDR:**
Can update the billing subscription interval for a subscription with a
base product and metered product. It also updates correctly as the
quantity of base products depending on how many people are in the
workspace.
**In order to test:**
1. Have the environment variable IS_BILLING_ENABLED set to true and add
the other required environment variables for Billing to work
2. Do a database reset (to ensure that the new feature flag is properly
added and that the billing tables are created)
3. Run the command: npx nx run twenty-server:command
billing:sync-plans-data (if you don't do that the products and prices
will not be present in the database)
4. Run the server , the frontend, the worker, and the stripe listen
command (stripe listen --forward-to
http://localhost:3000/billing/webhooks)
5. Buy a subscription for the Acme workspace , change the interval in
the Billing Settings
6. Add another person to the workspace, you should see all the previous
changes reflected in the database
**Doing**
Moving the BillingSubscriptionsService.getUpdatedSubscriptionItems to an
util (for a less cluttered service)
f58f84114c