Add package for onboarding

[amrit110]

This pull request introduces the initial implementation of the aieng-platform-onboard package, a CLI tool for onboarding participants to AI Engineering bootcamps. It includes a new workflow for publishing to PyPI, updates the package configuration, and adds the main utility module for onboarding automation. The most significant changes are grouped below:

Packaging and Distribution:

• Added a GitHub Actions workflow (.github/workflows/publish.yml) to automate building, verifying, and publishing the package to PyPI, and to create GitHub releases with installation and usage instructions.
• Updated pyproject.toml to rename the package to aieng-platform-onboard, provide a more accurate description, configure the CLI entry point (onboard), and set up packaging rules for both wheels and source distributions. [1] [2]

Core Implementation:

• Added src/aieng_platform_onboard/__init__.py to define the package and expose the CLI entry point.
• Introduced src/aieng_platform_onboard/utils.py, providing shared utilities for onboarding scripts, including:
  • Functions for interacting with GCP Secret Manager and Firestore to fetch tokens and participant/team/global data.
  • Methods for exchanging Firebase tokens, initializing authenticated Firestore clients, and updating participant onboarding status.
  • Utility for generating .env files with the required API keys and configuration.
  • Rich console output for user feedback and error reporting.