Proposal

Extend metrics API scaler to support Prometheus format, or new scaler would be preferable?

I'm thinking something like

triggers:
- type: metrics-api
  metadata:
    targetValue: "8"
    url: "http://api:3232/api/v1/stats?format=prometheus"
    valueLocation: "go_memstats_mcache_inuse_bytes"

or instead of relying on ?format we can also rely on content-type: application/json will use gjson and content-type: text/plain will use Prometheus format.

unfortunately most of /metrics mostly use content-type: text/plain instead of explicitly saying it's Prometheus

Use-Case

Currently, metrics API Scaler only support JSON format which is pretty handy if the application exposes metrics using JSON.

but most application currently exposes metrics using Prometheus Metrics format, for example.

Anything else?

I can work on this, in case this feature would be something acceptable