[kube-prometheus-stack] Implement Gateway API

[jkroepke]

What this PR does / why we need it

The current template is just an approach. Once finalized, we add it anywhere in the chart.

Ref: #4622

Which issue this PR fixes

(optional, in fixes #<issue number>(, fixes #<issue_number>, ...) format, will close that issue when PR gets merged)

• fixes #

Special notes for your reviewer

Checklist

• DCO signed
• Chart Version bumped
• Title of the PR starts with chart name (e.g. [prometheus-couchdb-exporter])

[QuentinBisson]

Do you have other examples of this kind of flag upstream? Because gateway is used for a lot of other things right now liké Mimir gateways so maybe other upstream projects use better names liké gatewayapi? It could also be they use gateway😅

[jkroepke]

No. I found nothing via GitHub Code search. Bitnami and Grafana did not have Gateway API yet, but I'm open for other names here.

But gatewayApi sounds more specific.

[rouke-broersma]

I would propose to skip the gateway level and use the httpRoute level only, this makes sense with gateway api terminology where the gateway resource is managed centrally by the cluster operator and the application developer only deals with routes. Alternatively if the extra level is needed because you envision that tlsRoute etc might also at some point be supported I would propose the following structure:

routes:
  http:
  tls:
  grpc:

...

But for a start I would suggest to keep it simple and start with:

httpRoute:
...

And if more route types are needed we can always introduce a breaking change at that point.

[jkroepke]

Still prefix the values with gatewayAPI - who knows what comes?

Currently, only httpRoute is implemented and there are no plans to provide more.

Let me know, if that current design is good to go