feat: add possibility of binding secret onto a different namespace

[ricogu]

Summary

This PR introduces the possibility of binding secrets to a different namespace in the crossplane-gardener-shoot-clusters Helm chart.

Changes

• Secret Namespace Configuration

  • Added support for specifying a custom secretNamespace for shoot clusters.
    • admin-kubeconfig-request.yaml template now uses .Values.shootClusters[].secretNamespace (defaults to "default" if not set).
    • Added secretNamespace field to both values.yaml and values.ci.yaml.

• YAML Cleanup

  • Removed extra whitespace lines from manifest templates for AWS, Azure, and GCP shoot clusters.

Motivation

• Enables users to bind connection secrets to custom namespaces.
• Improves documentation and template clarity.

Impact

• Existing clusters remain unaffected if they use the default namespace.
• New clusters can specify their own secret binding namespace.

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View the PR on GitHub

[sk31337]

@ricogu looks very good for the initial contribution. Please change the hierarchy of secretNamespace to the following everywhere:

    adminKubeconfigRequest:
      secretNamespace: ""

[ricogu]

@sk31337 , thanks for the review. I have adjusted the template, please have a look