Add Username to Audit Logs Generated with API Requests

[zackcl]

Is your feature request related to a problem? Please describe.
Currently, the audit logs generated with API requests (e.g., create/delete experiment) don't have a username since the requests are made using an access token generated with a service account.

Describe the solution you'd like
The audit logs generated with API requests should display the specific account user in some way (e.g., service account ID).

Additional context
Related issue: #1413 (closed)