Add CONTRIBUTING.md to provide guidelines for contributors

Author: Nico Thomaier

CONTRIBUTING.md

@@ -0,0 +1,184 @@
+## Welcome Contributors! 🎉
+
+Thank you for your interest in contributing to the Office365-REST-Python-Client library. This project provides a comprehensive Python client for Microsoft 365 and Microsoft Graph APIs.
+
+## Table of Contents
+
+1. Getting Started
+2. Development Environment Setup
+3. Code Style and Quality Standards
+4. Testing Guidelines
+5. Submitting Changes
+6. Issue Reporting
+7. Documentation
+8. Community Guidelines
+
+## Getting Started
+
+### Prerequisites
+
+- Python 3.6+
+- Git
+- A Microsoft 365 tenant for testing (recommended)
+- Basic understanding of REST APIs and Microsoft Graph/SharePoint APIs
+
+### Fork and Clone
+
+1. Fork the repository on GitHub
+2. Clone your fork locally:
+
+```bash
+git clone https://github.com/your-username/Office365-REST-Python-Client.git
+cd Office365-REST-Python-Client
+```
+
+## Development Environment Setup
+
+### Virtual Environment
+
+```bash
+python3 -m venv venv
+. venv/bin/activate  # On Windows: venv\Scripts\activate
+```
+
+### Install Dependencies
+
+```bash
+pip install -r requirements.txt
+pip install -r requirements-dev.txt
+```
+
+### Pre-commit hooks (recommended)
+
+```bash
+pip install pre-commit
+pre-commit install
+pre-commit run -a
+```
+
+## Code Style and Quality Standards
+
+The project uses the following tools (mirroring CI):
+
+- Black (formatting)
+- Ruff (linting and import sorting)
+- Pylint (static analysis)
+
+Line length: 121 characters (configured in `pyproject.toml`).
+
+Run locally before pushing:
+
+```bash
+black .
+ruff check .
+pylint office365
+```
+
+## Testing Guidelines
+
+Most tests are end-to-end and require actual Microsoft 365 credentials.
+
+### Test Configuration
+
+1. Create a `.env` file in the project root:
+
+```bash
+export office365_python_sdk_securevars='{username};{password};{client_id};{client_secret}'
+```
+
+2. Source the environment file:
+
+```bash
+. .env
+```
+
+Note: The order of values is significant because tests parse by index.
+
+### Required Tenant Permissions
+
+For comprehensive testing, your test tenant should have these admin roles:
+
+- Global reader
+- Groups admin
+- Search admin
+- SharePoint admin
+- Teams service admin
+
+### Running Tests
+
+```bash
+pytest
+# or
+pytest -v
+# or a specific suite
+pytest tests/sharepoint/
+```
+
+CI note: Full E2E tests in CI rely on repository secrets and may not run on forks. Please run tests locally; maintainers trigger full CI runs as needed.
+
+### Forks and CI
+
+- Forked pull requests do not receive repository secrets. The CI pipeline will run formatting and linting, and it will skip `pytest` automatically if secrets are unavailable.
+- To validate your changes, run tests locally using your own tenant credentials as described above.
+- Maintainers will run the full E2E test suite on branches with access to secrets before merging.
+
+## Submitting Changes
+
+### Branching Strategy
+
+1. Create a feature branch from `master`:
+
+```bash
+git checkout -b feature/your-feature-name
+```
+
+2. Make your changes with clear, focused commits
+3. Ensure all tests pass and quality checks are satisfied
+
+### Pull Request Process
+
+1. CI Checks must pass:
+   - Ruff linting
+   - Black formatting
+   - Pylint analysis
+   - Pytest execution
+2. Await maintainer review
+3. Update documentation where applicable
+
+### Commit Guidelines
+
+- Use clear, descriptive commit messages
+- Reference issue numbers when applicable
+- Keep commits focused and atomic
+
+## Issue Reporting
+
+Before filing an issue:
+
+1. Search existing issues
+2. Check documentation and examples
+3. Test with the latest version
+
+Include in your report:
+
+- Environment: Python version, OS, library version
+- Reproduction: minimal code example
+- Expected vs Actual behavior
+- Authentication method used
+- Targeted service area (SharePoint, Graph, etc.)
+
+## Documentation
+
+### API Coverage
+
+The library supports multiple Microsoft 365 APIs, including SharePoint REST, Microsoft Graph, OneDrive, Outlook, Teams, OneNote, and Planner. See `examples/` for usage.
+
+## Community Guidelines
+
+This project is maintained by the community. Be respectful and constructive in all interactions.
+
+### License
+
+MIT License. By contributing, you agree that your contributions are licensed under these terms.
+
+