This pull request introduces significant improvements to the documentation, testing, and deployment workflows for the project, as well as several codebase and configuration updates. The most important changes are grouped below by theme.

Documentation and onboarding improvements:

• The README.md has been extensively rewritten to provide clearer, step-by-step onboarding instructions, improved explanations of domain and multi-tenant configurations, and enhanced guidance for development and debugging. The manifest example has been updated to reflect new configuration keys and best practices. [1] [2] [3] [4] [5]

Testing and CI enhancements:

• Added a GitHub Actions workflow (.github/workflows/test.yml) to automate testing on push and pull requests to main, including Slack notifications for failures.
• Introduced a phpunit.xml configuration file to enable PHPUnit-based testing.
• Updated composer.json to add Pest as a dev dependency, configure Pest plugin support, and move Spatie Ray to dev dependencies. [1] [2]

Codebase and deployment workflow changes:

• Refactored BuildCommand and DeployCommand to inherit from SteppedCommand, simplifying their structure and progress output handling. [1] [2] [3] [4] [5] [6]
• Updated deployment steps to use SyncStandaloneRecordSetStep for standalone apps, clarifying deployment logic.

Configuration and manifest updates:

• Expanded manifest configuration options to include keys such as account-id, vpc, artefacts-bucket, key-pair, and multi-tenant domain settings, supporting more flexible AWS setups. [1] [2]

Code quality and AWS integration improvements:

• Improved AWS helper methods, including a more flexible tags method and updated accountId retrieval using manifest values. [1] [2]
• Minor code fixes and improvements for AWS client imports and environment profile checks. [1] [2] [3] [4] [5]

These changes collectively improve the project's usability, reliability, and maintainability.