I posted a video on the Power BI YouTube channel for using PowerShel and the Audit log to assign Power BI Pro licenses. In this video, I give you a few other options instead of automating off of the audit log.

Main video:
Using Power BI Audit Log and PowerShell to assign Power BI Pro licenses – https://youtu.be/oulR910VBrU
Full Blog with PowerShell script
https://powerbi.microsoft.com/en-us/blog/using-powershell-and-the-audit-log-to-assign-power-bi-pro-licenses/