Add Helm chart for Alertmanager-Icinga-Bridge deployment

[smallc2009]

This pull request introduces a new Helm chart for deploying the alertmanager-icinga-bridge application on Kubernetes. The chart includes all the necessary templates, configuration files, and a GitHub Actions workflow for automated chart releases. The most important changes are grouped below:

Helm Chart Introduction and Structure

• Added a new Helm chart for alertmanager-icinga-bridge, including metadata (Chart.yaml), default values (values.yaml), and helper template functions (_helpers.tpl). This provides a standardized, configurable way to deploy the application on Kubernetes. [1] [2] [3]

Kubernetes Resource Templates

• Implemented templates for key Kubernetes resources:
  • Deployment (deployment.yaml): Configurable environment, secret references, probes, and support for extra volumes and affinity.
  • Service (service.yaml): Exposes the application via a ClusterIP service.
  • ServiceAccount (serviceaccount.yaml): Optionally creates a dedicated service account with custom annotations.
  • Secrets (secret.yaml, pull-secret.yaml): Manages sensitive data for Icinga and Alertmanager credentials, and optionally creates Docker registry pull secrets. [1] [2]

CI/CD Automation

• Added a GitHub Actions workflow (release-chart.yml) to automate chart releases when changes are pushed to the main branch and files under charts/** are updated.