## Context This task migrates the Audit system to use `identifier` instead of `username` for authentication. This ensures consistent and reliable identification of actors (users and deploy tokens) in audit events. The Audit system currently relies on the `username` field for authentication. This task is part of a larger effort to improve how deploy tokens are handled in Git streaming audit events. ## Plan 1. [Introduce a `deploy-token-{id}` identifier](https://gitlab.com/gitlab-org/gitlab/-/issues/570235) 2. [Fix GlId generation for `DeployToken`](https://gitlab.com/gitlab-org/gitlab/-/blob/7642b57f7da500bf5007dc6d17727ca289b47903/lib/gitlab/workhorse.rb#L29) 3. **Migrate the Audit system from using `username` for authentication to use `identifier`** (this task) ## Key Changes * Update the Audit system to use the `identifier` field instead of `username` for actor identification * Ensure deploy tokens are properly identified with the `deploy-token-{id}` format * Maintain consistency across audit event tracking ## References * Parent issue: #562516 - Fix authentication parameters for Git streaming audit events HTTP requests * Related task: #570235 - Introduce a deploy-token-{id} identifier