[Feature Request] - Metrics endpoint

[vyrtualsynthese]

Hi,

It would be greate to have some /metrics exposted to be consumed by Prometheus. https://github.com/promphp/prometheus_client_php

Usefull metrics could be :

• Registered user count
• Allowed Disk space Global
• Used Disk space Global
• Allowed disk space per users
• Used disk space per users
• Number of collections, lists, items

As most of your metrics are already in statistics but from an admin point of view.