Template automation (#12)

* Add initial setup for pytest and GitHubClient tests

- Created pytest configuration file `pytest.ini` for test discovery and options.
- Added `requirements.txt` for project dependencies including testing libraries.
- Introduced `test_payload.json` for storing test data related to EKS settings.
- Established a test package with `__init__.py` in the `tests` directory.
- Implemented fixtures in `conftest.py` for mocking GitHub API responses.
- Developed unit tests for `GitHubClient` methods in `test_github_client.py`.
- Created integration tests for `GitHubClient` in `test_github_client_integration.py`.
- Added environment cleanup fixture to ensure a clean state for tests.
- Implemented unit tests for application logic in `test_app.py`, including SSM parameter retrieval and GitHub operations.

* Refactor GitHub token handling to use GITHUB_TOKEN_SECRET_NAME

* Add team-based admin access feature to GitHubClient and integration tests

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Co-authored-by: Dave Arnold <dave@roknsound.com>