feat(helm): add HPA extra metrics

[AdrienPoupa]

Append additional HPA metrics to the rendered HorizontalPodAutoscaler on top of the chart's existing CPU/memory Resource metrics.

This unblocks scaling the router on external/custom metrics provided by adapters such as Prometheus Adapter, KEDA, or Datadog Cluster Agent.

Summary by CodeRabbit

• New Features

  • Router autoscaling now supports injecting additional custom metrics for flexible scaling policies that extend beyond the default CPU and memory utilization metrics.

• Documentation

  • Updated documentation for router autoscaling configuration options and custom metrics support.

Checklist

• I have discussed my proposed changes in an issue and have received approval to proceed.
• I have followed the coding standards of the project.
• Tests or benchmarks have been added or updated.
• Documentation has been updated on https://github.com/wundergraph/docs-website.
• I have read the Contributors Guide.

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[claude]

Claude Code Review

This pull request is from a fork — automated review is disabled. A repository maintainer can comment @claude review to run a one-time review.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro

Run ID: b4838ed0-45af-46f6-8a45-10b4ef26c1fc

📥 Commits

Reviewing files that changed from the base of the PR and between 992b6c6 and 31702e4.

📒 Files selected for processing (3)

• helm/cosmo/charts/router/README.md
• helm/cosmo/charts/router/templates/hpa.yaml
• helm/cosmo/charts/router/values.yaml

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Walkthrough

This PR extends the router Helm chart to support custom autoscaling metrics via a new autoscaling.extraMetrics configuration. The values schema defines the empty-list default, the HPA template renders these metrics into the Kubernetes spec, and the README documents the new parameter.

Changes

Extra Metrics Configuration for Router HPA

Layer / File(s)	Summary
Configuration Schema helm/cosmo/charts/router/values.yaml	autoscaling.extraMetrics is added as an empty list with documentation specifying entries must be full autoscaling/v2 metric objects to append to the HPA metrics list.
Template Rendering helm/cosmo/charts/router/templates/hpa.yaml	HPA template now includes an extraMetrics rendering block under spec.metrics that outputs user-supplied YAML with proper indentation.
Values Documentation helm/cosmo/charts/router/README.md	autoscaling.extraMetrics is documented in the values table as a list type with default empty array.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~8 minutes

Possibly related PRs

• wundergraph/cosmo#2798: Both PRs extend the router Helm chart HPA template; this PR adds support for custom autoscaling.extraMetrics while that PR adds support for spec.behavior and startup probe configuration.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title 'feat(helm): add HPA extra metrics' directly summarizes the main change: adding support for extra HPA metrics to the Helm router chart.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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[pepol]

LGTM