Add prometheus monitoring for CouchDB

[kennsippell]

CouchDB v3.2 includes a prometheus endpoint.

We should do something like:

• Check that it is safe to make this a non-authenticated endpoint (seems fine at first glance)
• Turn it on as non-authenticated endpoint. Details
• Scrape it via prometheus (unclear on what the value of {node-name} will be in the url)
• Add some default dashboards. This example looks just okay, but is the most popular.