feat(rules): when naming rules files use clear namespace separation

[diranged]

Description

Ref: #3468

I ran into the same issue that @janotav did with this comment. I want to be able to identify metrics from the Thanos Ruler around rule execution and failures and narrow them down to the Namespace and PrometheusRule that they come from. The problem is the current naming pattern of $namespace-$rulename-$uid doesn't account for resources that have -'s in the names... ie, the following rule creates a file named my-namespace-some-rule-thing-xxx-xxx-xxx-xxx-xxx:

apiVersion: monitoring.coreos.com/v1
kind: PrometheusRule
metadata:
  name: some-rule-thing
  namespace: my-namespace
  resourceVersion: "1146"
  uid: xxx-xxx-xxx-xxx-xxx

The string my-namespace-some-rule-thing-xxx-xxx-xxx-xxx-xxx cannot be parsed through metric relabelings because you cannot definitively pull out the namespace and name fields from the filename.

Type of change

• CHANGE (fix or feature that would cause existing functionality to not work as expected)
• FEATURE (non-breaking change which adds functionality)
• BUGFIX (non-breaking change which fixes an issue)
• ENHANCEMENT (non-breaking change which improves existing functionality)
• NONE (if none of the other choices apply. Example, tooling, build system, CI, docs, etc.)

Verification

Due to #6284 - I was unable to fully test this locally.

Changelog entry

Please put a one-line changelog entry below. This will be copied to the changelog file during the release process.

Use "--" to separate namespace, resource name and UID in Prometheus Rules filenames

[diranged]

I see that these tests (https://github.com/prometheus-operator/prometheus-operator/actions/runs/8577200973/job/23509431752?pr=6482) failed - but I can't see how they relate to my change. Could they be flakey?

[simonpasquier]

I agree that it'd be useful to reverse-parse the rule's namespace/name but if we do this, it should be documented somewhere. We could also discuss what should be used to separate namespace and name.
cc @prometheus-operator/prometheus-operator-reviewers

[diranged]

@simonpasquier This is 3 weeks old now - thoughts on what we can do here to move this along?

[simonpasquier]

I'm not 100% fan of the -- separator, could we use , to have a single char separator?

[diranged]

I don't really care what the separator is ... but I've just seen -- used in other places. I can't say I am a fan of a , in a filename.. either way though, it does actually work. If you want me to use a , that's fine with me I guess,..