Update prometheus config to include the new metrics endpoint

[josecelano]

Relates to: #36

global:
  scrape_interval: 15s # How often to scrape metrics

scrape_configs:
  - job_name: "tracker_stats"
    metrics_path: "/api/v1/stats"
    params:
      token: ["MyAccessToken"]
      format: ["prometheus"]
    static_configs:
      - targets: ["tracker:1212"]

  - job_name: "tracker_metrics"
    metrics_path: "/api/v1/metrics"
    params:
      token: ["MyAccessToken"]
      format: ["prometheus"]
    static_configs:
      - targets: ["tracker:1212"]

NOTICE: No metrics with the same names exist, so we do not need to relabel configs (relabel_configs section).

[josecelano]

This will require updating the Prometheus config file.

ssh demo
cd github/torrust/torrust-demo/ 
vim storage/prometheus/etc/prometheus.yml