Add id-labels flag

[gbbirkisson]

Add flag to set global id-labels on generated recording and alert rules:

$ sloth generate -i slo.yaml --id-labels=env=dev

These labels will be used for generated queries and added as labels as well. This will result in recording rules looking like this:

expr: |
  slo:sli_error:ratio_rate5m{env="dev", sloth_id="???", sloth_service="???", sloth_slo="???"}
  / on(sloth_id, sloth_slo, sloth_service) group_left
  slo:error_budget:ratio{env="dev", sloth_id="???", sloth_service="???", sloth_slo="???"}
labels:
  env: dev
  sloth_id: ???
  sloth_service: ???
  sloth_slo: ???

Alerts will also inherit these id labels:

alert: Alertname
expr: |
  (
      max(slo:sli_error:ratio_rate5m{env="dev", sloth_id="???", sloth_service="???", sloth_slo="???"} > (14.4 * 0.9)) without (sloth_window)
      and
      max(slo:sli_error:ratio_rate1h{env="dev", sloth_id="???", sloth_service="???", sloth_slo="???"} > (14.4 * 0.9)) without (sloth_window)
  )
  or
  (
      max(slo:sli_error:ratio_rate30m{env="dev", sloth_id="???", sloth_service="???", sloth_slo="???"} > (6 * 0.9)) without (sloth_window)
      and
      max(slo:sli_error:ratio_rate6h{env="dev", sloth_id="???", sloth_service="???", sloth_slo="???"} > (6 * 0.9)) without (sloth_window)
  )
labels:
  env: dev

[thor]

SGTM. Tempted to create a separate struct for handling the labels as extra labels and ID labels seem to go together most of the time, but I don't think that's a blocker here. 🚀

[torvald]

Nice! This will do! It will not fix the issue were the tier label changes, I think, I presume we need to alter the queries for that, ignoring tier, or a set of ignoreLabels. But one thing at a time. 👏