adds /metrics endpoint with prometheus format

[michbeck100]

No description provided.

[benni336]

Hi Michael,

I once did a commit for an JSON-Export. But I put it into it's own export method.
That had the advantage that it was configureable via the config.py and looks more like a "plugin".
But it has also disadvantage: code duplication, and it needs to run on its own port.

I think it would be a nice step to "choose",

• wether one want one "http text export" leading to sub directories like /json or /metrics and the html export.
• or wether one want a "plugin style" solution, like http-webserver, mqtt-export, pvOutput and also JSON and Prometheus export.

Just as a remark.

Greetings from Cologne, DE

[michbeck100]

I think the code duplication is a problem. That's why I just used the /metrics endpoint of the http-webserver. I think this does not need any notable resources.

[bohdan-s]

Looks good! Might change this to /api/v1/ in the future