[usage] Add billInstancesAfter config setting

[andrew-farries]

Description

Add a new config setting to the usage component config setting to better support the rollout of usage based pricing.

The billInstancesAfter setting defines the date after which instances should be considered for billing - instances started before billInstancesAfter will never be considered by the billing controller.

Related Issue(s)

Part of #10937

How to test

Unit tests for the billing controller.

For an end-to-end test do this in the preview environment:

• Join the Gitpod team: https://af-no-bill390c0e761d.preview.gitpod-dev.com/teams/join?inviteId=f35adc3b-720f-4406-85ec-101628b587bc

• Edit the usage configmap to change billInstancesAfter:

{
  "billInstancesAfter": "2022-08-06T00:00:00Z",
  ...
}

By changing the date, restarting the usage pod and starting workspaces you can see that workspaces are either included or not in the Stripe invoice for the Gitpod team (find it in the Stripe dashboard).

Release Notes

NONE

Documentation

Werft options:

• /werft with-preview
• /werft with-payment

[andrew-farries]

/werft run

👍 started the job as gitpod-build-af-no-billing-for-old-instances.9
(with .werft/ from main)

[geropl]

Code LGTM, tested and works - nice! 🎉

Out-of-scope, but may be relevant for later: We noticed that if there is 0 usage, the BillingController does not call Stripe to override the old state. It's an edge case, but we have to be aware.