Implement monitoring for Apache James server

[ieugen]

When running in production, we need to have a monitoring solution in place.

The latest and greatest monitoring solution is Prometheus https://prometheus.io/docs/introduction/overview/ .
Let's see if we can use Prometheus or not.

[chibenwa]

Overall 👍 for this work, we should consider exposing the metrics via HTTP to make it gaverable by prometheus. But I would prefer us to open an Apache James JIRA for this.

[chibenwa]

https://issues.apache.org/jira/browse/JAMES-3405 will please you:

curl -XGET http://127.0.0.1:8000/metrics returns metrics that can be collected by prometheus.

We will document how to set the all stack up.

[ieugen]

Thanks.
I will check it out once I get back to email.