Improvements and refactoring of shared actions

[habakke]

Description

This pull request introduces several improvements and refactorings to the shared GitHub Actions repository, focusing on documentation, reliability, and maintainability of composite actions for CI/CD workflows. The most significant changes include a major rewrite of the README.md for clarity and onboarding, the addition of a shared JavaScript module for posting Terraform plan results to PR comments, and updates to authentication actions for better input validation and support for modern best practices.

Documentation and onboarding improvements:

• Major rewrite of README.md to provide a comprehensive overview of available actions, usage examples, onboarding instructions, and prerequisites, making it easier for new users to understand and adopt the repository.

Terraform workflow enhancements:

• Added _shared/terraform-pr-comment.js, a shared module to reliably post Terraform plan results to PR comments, featuring smart updates, size management, security/destroy warnings, and platform-specific branding. This module is designed for reuse across GCP and OpenStack actions, reducing code duplication. [1] [2]

Authentication action improvements:

• Refactored auth-gcp-action/action.yml to validate inputs and support both service account key and workload identity federation, updating dependencies to use the latest versions of Google authentication and setup actions.
• Created a new auth-github-action/action.yml with input validation and clear documentation for authenticating to GitHub Container Registry, replacing the previous implementation.

Security and reliability updates:

• Removed legacy composite action definitions for authentication and Docker security scanning (.github/actions/auth-github/action.yml, .github/actions/docker-security-scan/action.yml) to reduce duplication and enforce use of updated, validated actions. [1] [2]

Release workflow refinements:

• Improved the release workflow in .github/workflows/release.yml by clarifying input descriptions, updating action references, and adding a job summary step for better visibility of release metadata. [1] [2]

Change management

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[Copilot]

Pull Request Overview

This pull request enhances the shared GitHub Actions repository by consolidating actions from .github/actions/ to root-level directories, improving documentation with a comprehensive README, and adding a shared JavaScript module for Terraform PR comments. The changes focus on better organization, input validation, and code reuse across actions.

• Moved composite actions from .github/actions/ to root directories for better organization
• Added comprehensive README with usage examples and prerequisites
• Created shared terraform-pr-comment.js module to eliminate code duplication between GCP and OpenStack Terraform actions

Reviewed Changes

Copilot reviewed 16 out of 16 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
terraform-deploy-openstack-action/action.yml	Updated to use shared PR comment module and improved input validation
terraform-deploy-gcp-action/action.yml	Updated to use shared PR comment module and improved input validation
release-action/action.yml	Enhanced with input validation and better parameter handling
examples/*.yml	Updated to reference new action paths and improved configuration
docker-security-scan-action/action.yml	New consolidated action with input validation
docker-build-action/action.yml	Enhanced with input validation and conditional GCP setup
auth-github-action/action.yml	New consolidated GitHub authentication action
auth-gcp-action/action.yml	Enhanced with workload identity support and input validation
_shared/terraform-pr-comment.js	New shared module for Terraform PR comments with enhanced features
_shared/README.md	Documentation for shared modules
README.md	Comprehensive rewrite with usage examples and prerequisites
.github/workflows/release.yml	Updated to use new action path and added job summary
.github/actions/docker-security-scan/action.yml	Removed legacy action
.github/actions/auth-github/action.yml	Removed legacy action

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