docs: Refresh configuration walkthrough

[aland-omed]

Fixes #679.

Updates the configuration walkthrough to match the API version and response schema used by the repository’s current end-to-end walkthrough and generated OpenAPI definitions.

Changes:

• use custom.metrics.k8s.io/v1beta2 endpoints and discovery data
• show v1beta2 metric.name response objects instead of v1beta1 metricName
• remove obsolete selfLink and /__internal output
• make discovery names consistent with the configured _per_second rename
• correct the standalone PromQL query and nearby wording

Validation:

• both JSON response examples parse successfully
• git diff --check
• Markdown lint reports only three pre-existing style warnings on unchanged lines

[linux-foundation-easycla]

• ❌ - login: @aland-omed / name: Aland. The commit (1bd476f) is not authorized under a signed CLA. Please click here to be authorized. For further assistance with EasyCLA, please visit our EasyCLA portal and chat with our support bot.

[kubernetes-prow]

This issue is currently awaiting triage.

If prometheus-adapter contributors determine this is a relevant issue, they will accept it by applying the triage/accepted label and provide further guidance.

The triage/accepted label can be added by org members by writing /triage accepted in a comment.

Details

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes-sigs/prow repository.

[kubernetes-prow]

Welcome @aland-omed!

It looks like this is your first PR to kubernetes-sigs/prometheus-adapter 🎉. Please refer to our pull request process documentation to help your PR have a smooth ride to approval.

You will be prompted by a bot to use commands during the review process. Do not be afraid to follow the prompts! It is okay to experiment. Here is the bot commands documentation.

You can also check if kubernetes-sigs/prometheus-adapter has its own contribution guidelines.

You may want to refer to our testing guide if you run into trouble with your tests not passing.

If you are having difficulty getting your pull request seen, please follow the recommended escalation practices. Also, for tips and tricks in the contribution process you may want to read the Kubernetes contributor cheat sheet. We want to make sure your contribution gets all the attention it needs!

Thank you, and welcome to Kubernetes. 😃

[kubernetes-prow]

Hi @aland-omed. Thanks for your PR.

I'm waiting for a kubernetes-sigs member to verify that this patch is reasonable to test. If it is, they should reply with /ok-to-test on its own line. Until that is done, I will not automatically test new commits in this PR, but the usual testing commands by org members will still work.

Regular contributors should join the org to skip this step.

Once the patch is verified, the new status will be reflected by the ok-to-test label.

I understand the commands that are listed here.

Details

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes-sigs/prow repository.

[kubernetes-prow]

[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by: aland-omed
Once this PR has been reviewed and has the lgtm label, please assign dgrisonnet for approval. For more information see the Code Review Process.

The full list of commands accepted by this bot can be found here.

Details

Needs approval from an approver in each of these files:

• OWNERS

Approvers can indicate their approval by writing /approve in a comment
Approvers can cancel approval by writing /approve cancel in a comment