INFO level logs for license confirmation

[JTorreG]

Customer report:

Your documentation mentions error messages to watch for https://docs.nginx.com/solutions/about-subscription-licenses/#log-monitoring
Is there a "positive log" that would tell that the reporting worked properly? Ideally we would like a prometheus metric for this too
The positive log is undocumented as far as I can see, and required the info log level (we were using warn)
Would you be able to improve the documentation on this?

AC: The licensing page should include steps to confirm the license is working properly by enabling INFO logs.