Prometheus metrics

[jpds]

The WAF level should expose Prometheus metrics the same way Caddy does, some useful base metrics would be:

• Total number of rules loaded
• Total number of times a request was blocked

[jcchavezs]

Thanks for coming by. We introduced this set of metrics in proxy-wasm corazawaf/coraza-proxy-wasm#29 and there is this other discussion around metrics in coraza itself corazawaf/coraza#774.

I think given the interest we should be able to either have here what we have in proxy-wasm or have a discussion around what would be better set of metrics. I would also love to involve @azurit and @airween to get some inputs on what good set of metrics for a WAF look like.

[azurit]

I don't think i am able to add anything valuable into this discussion.