Implement GitHub Actions Pipeline for ArgoCD Agent Deployment

[USHER-PB]

OBJECTIVE

Create a robust CI/CD pipeline using GitHub Actions to automate the deployment of the ArgoCD Hub-and-Spoke architecture using the existing Terraform scripts in argocd-agent/terraform/environments/prod.

Scope:

Directory: argocd-agent/terraform/environments/prod
Architecture: Orchestrates the deployment of a Hub Cluster (Control Plane) and multiple Spoke Clusters (Agents).
Key Modules: hub_cluster, and spoke_cluster.
Tasks:

• Workflow Configuration:
  Trigger the pipeline on push to the main branch or via workflow_dispatch.
  Add a terraform-plan job to run on Pull Requests.
• Infrastructure Initialization:
  Install required tools: Terraform, kubectl, helm, and the argocd-agentctl binary.
  Configure Terraform remote backend (update backend.tf to use S3/GCS for state persistence).
• Authentication & Secrets:
  Securely inject Kubernetes credentials (Kubeconfig) for both Hub and Spoke clusters.
  Manage Keycloak administrative credentials as GitHub Secrets.
  Configure cloud provider credentials for Terraform state management.
• Deployment Logic:
  Execute terraform init, terraform plan, and terraform apply.
  Support dynamic deployment modes (deploy_hub, deploy_spokes) via variable inputs.
• Validation:
  Implement a post-deployment check to verify the ArgoCD Agent's connectivity.