feat(billable events): pass instance uid to billable event

Alejandro Rodríguezrequested to merge
billing-events-unique-instance-id into main

What does this merge request do and why?

Part of https://gitlab.com/gitlab-org/architecture/usage-billing/design-doc/-/issues/16

How to set up and validate locally

This code is not yet invoked in runtime, so there's no validation to be done at the moment, this is still preparation work. See https://gitlab.com/groups/gitlab-org/-/epics/18586+ for more context.

Merge request checklist

  • Tests added for new functionality. If not, please raise an issue to follow up.
  • Documentation added/updated, if needed.
  • If this change requires executor implementation: verified that issues/MRs exist for both Go executor and Node executor or confirmed that changes are backward-compatible and don't break existing executor functionality.

Merge request reports