Add prometheus exporter and grafana dashboard for mailcow.

[Hassanzadeh-sd]

Contribution Guidelines

• I've read the contribution guidelines and wholeheartedly agree them

What does this PR include?

Short Description

This PR adds a Prometheus exporter and Grafana dashboard for mailcow. Key changes:

Prometheus Exporter: Collects mailcow metrics for monitoring. Requires enabling the mailcow API and generating an API key.
/metrics Endpoint: Exposes metrics for Prometheus to scrape.
Grafana Dashboard: Visualizes key mailcow metrics for easy monitoring.

How to use:

Enable the Mailcow API and create a read-only API key.
Configure the exporter with your mailcow host and API key.
Import the provided Grafana dashboard to visualize the metrics.

This makes it easier to monitor your Mailcow instance with Prometheus and Grafana.

Affected Containers

nothing it is an override compose file.

Did you run tests?

What did you tested?

I tested the Prometheus exporter and Grafana dashboard integration with my own Mailcow services. I verified that:

The exporter successfully collected metrics from the mailcow API.
The metrics were exposed correctly via the /metrics endpoint.
Prometheus could scrape the metrics endpoint without errors.
The Grafana dashboard visualized the collected metrics accurately and effectively.

The exporter and dashboard have been running in my environment and functioning as expected since testing.

What were the final results? (Awaited, got)

All tests passed successfully. I expected the exporter to accurately collect and expose mailcow metrics in Prometheus format, and the Grafana dashboard to visualize these metrics effectively. The outcome matched my expectations, providing a functional monitoring solution for mailcow.

[Hassanzadeh-sd]

I hope you are doing well. I wanted to kindly follow up regarding my pull request submitted four days ago, I understand that the team is busy, but I would appreciate any feedback or updates regarding its status.

[DerLinkman]

Please read the contribution guidelines properly as your PR is not cleaned up and is not pointing to staging...

[Hassanzadeh-sd]

I'll fix it and send a new pr thank you.