Athens: Add Prometheus service to Athens docker-compose

[t-tomalak]

Is your feature request related to a problem? Please describe.
As we support metrics export to prometheus (#816) we could add it as a service to our docker-compose

Describe the solution you'd like

There should be configured prometheus service in Athens docker-compose that will be listening on Athens metrics endpoint

Additional context
https://hub.docker.com/r/prom/prometheus/
https://prometheus.io/docs/prometheus/latest/configuration/configuration/

[vaibhavjayaraman]

Can I give this a shot?

[t-tomalak]

Sure, go ahead!

[vaibhavjayaraman]

Sorry about the delay. I was busy with school work. I added a Prometheus service to the docker-compose file but I made a lot of hacky assumptions when writing the configuration file and updating the docker-compose file. Should I create a PR so that you guys can critic?

[michalpristas]

sure @vaibhavjayaraman feel free to raise a PR and comment places where you need input from somebody, or something is unclear

[vaibhavjayaraman]

Cool. I raised a PR and commented on lines that I had immediate issues with.