Refactor duplicated Kubernetes resources with reusable templates and tooling

[Copilot]

The repository contained significant duplication across VirtualService definitions (13 instances), NFS volume configurations (5 instances), and Kustomize patches (6+ service patches), making maintenance error-prone and onboarding difficult.

Changes

Reusable Templates (k8s-templates/)

• VirtualService templates (base and with URI rewriting) using clear placeholder syntax (<app-name>, <gateway>)
• NFS PersistentVolume/PersistentVolumeClaim template with configurable paths and storage classes
• Common Kustomize patches for service ports, deployment resources, and container ports

Example usage:

# Copy template and customize placeholders
cp k8s-templates/virtualservice-base.yaml applicationset/myapp/vs.yaml
# Replace <app-name> with actual application name

Documentation

• CONTRIBUTING.md - Complete workflow for adding applications with pattern examples
• k8s-templates/README.md - Template usage guide with copy-paste examples
• .github/workflows/README.md - Explains why individual workflows exist (isolated triggers, clear build status)
• Updated main README.md with "Adding a New Application" section

Tooling

• scripts/find-similar-files.sh - Identifies duplication candidates by grouping files with identical names, using null delimiters for safe filename handling

Bug Fix

• applicationset/toolchain/kustomization.yaml - Added missing vs.yaml resource reference

Impact

Templates provide starting point for new applications while existing implementations remain unchanged. The detection script enables periodic audits for new duplication patterns.

Original prompt

Find and refactor duplicated code

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