docs: Created CONTRIBUTING.md (#3)

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Author: askmanu[bot]

CONTRIBUTING.md

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+# Contributing to API Server
+
+> [!Note]
+> This is the API server component of the peermetrics WebRTC monitoring service. For the full project, see [peermetrics](https://github.com/peermetrics/peermetrics).
+
+We welcome contributions to the API server! This guide will help you set up your development environment and understand our contribution workflow.
+
+## Prerequisites
+
+Before you begin, ensure you have the following installed:
+
+- Python 3.8
+- PostgreSQL
+- Redis
+- pip
+- virtualenv (recommended)
+- Git
+
+## Local Development Setup
+
+### 1. Clone the Repository
+
+```bash
+git clone https://github.com/peermetrics/api-server.git
+cd api-server
+```
+
+### 2. Set Up Python Virtual Environment
+
+```bash
+python3 -m venv venv
+source venv/bin/activate  # On Windows: venv\Scripts\activate
+```
+
+### 3. Install Dependencies
+
+```bash
+pip install -r requirements.txt
+```
+
+### 4. Configure Environment Variables
+
+Copy the `.env` file and update the values as needed:
+
+```bash
+cp .env .env.local
+```
+
+Key environment variables to configure:
+
+- `DEBUG`: Set to `True` for development
+- `SECRET_KEY`: Django secret key
+- `INIT_TOKEN_SECRET`: Used to generate JWT tokens
+- `SESSION_TOKEN_SECRET`: Used to encrypt session cookies
+- `DATABASE_HOST`, `DATABASE_PORT`, `DATABASE_USER`, `DATABASE_PASSWORD`, `DATABASE_NAME`: PostgreSQL connection details
+- `REDIS_HOST`: Redis server location
+- `WEB_DOMAIN`: Domain for the web interface (default: `localhost:8080`)
+
+### 5. Set Up the Database
+
+Run Django migrations to create the database schema:
+
+```bash
+python manage.py migrate
+```
+
+### 6. Create a Superuser (Optional)
+
+To access the Django admin interface:
+
+```bash
+python manage.py createsuperuser
+```
+
+### 7. Populate Test Data
+
+Use the `populate_db.py` script to generate test data:
+
+```bash
+# Generate data for the last 7 days
+python populate_db.py 7
+
+# Clean all test data
+python populate_db.py clean
+```
+
+### 8. Run the Development Server
+
+```bash
+python manage.py runserver
+```
+
+The API will be available at `http://localhost:8000`.
+
+## Project Structure
+
+```
+api-server/
+├── api/                    # Django project settings
+│   ├── settings.py        # Main settings file
+│   └── urls.py            # Root URL configuration
+├── app/                   # Main application
+│   ├── models/           # Database models
+│   ├── views/            # API views/endpoints
+│   ├── middleware.py     # Custom middleware
+│   └── decorators.py     # Custom decorators
+├── static/               # Static files
+├── config_populate_db/   # Test data configuration
+├── manage.py             # Django management script
+├── populate_db.py        # Script to populate test data
+└── requirements.txt      # Python dependencies
+```
+
+### Key Files
+
+- **manage.py**: Standard Django management script for running commands
+- **populate_db.py**: Generates realistic test data for development
+- **config_populate_db**: Configuration files for test data generation
+
+### Models
+
+The main models are located in `app/models/`:
+
+- **Organization**: Groups multiple apps
+- **App**: Groups conferences
+- **Conference**: Represents a call between participants
+- **Participant**: A user participating in conferences
+- **Session**: A participant's presence in a conference
+- **GenericEvent**: Events collected during calls
+
+### Views
+
+API endpoints are organized in `app/views/` and split into:
+
+- **Public routes**: Used by the SDK (e.g., `/initialize`, `/events/*`, `/stats`)
+- **Private routes**: Used for data queries (e.g., `/sessions`, `/conferences`, `/participants`)
+
+## Development Workflow
+
+### 1. Create a New Branch
+
+```bash
+git checkout -b feature/your-feature-name
+```
+
+Use descriptive branch names:
+- `feature/` for new features
+- `fix/` for bug fixes
+- `docs/` for documentation changes
+
+### 2. Make Your Changes
+
+Follow these guidelines:
+
+- Write clear, self-documenting code
+- Add comments for complex logic
+- Keep functions focused and small
+- Follow Django best practices
+
+### 3. Test Your Changes
+
+Run the development server and test your changes manually:
+
+```bash
+python manage.py runserver
+```
+
+Use the Django admin interface at `http://localhost:8000/admin` to inspect data.
+
+### 4. Commit Your Changes
+
+Write clear commit messages:
+
+```bash
+git add .
+git commit -m "Add feature: brief description of changes"
+```
+
+Good commit message format:
+```
+Add feature: allow filtering conferences by date range
+
+- Added date_from and date_to query parameters
+- Updated Conference view to handle date filtering
+- Added validation for date format
+```
+
+## Django Admin Interface
+
+Access the admin interface at `http://localhost:8000/admin` to:
+
+- View and edit raw data
+- Inspect model relationships
+- Debug data issues
+- Manually create test records
+
+Login with the superuser credentials you created during setup.
+
+## API Development Guidelines
+
+### Adding New Endpoints
+
+1. Define the view in `app/views/`
+2. Add the URL pattern in `api/urls.py`
+3. Implement authentication/authorization if needed
+4. Test the endpoint manually
+
+### Model Changes
+
+When modifying models:
+
+```bash
+# Create migrations
+python manage.py makemigrations
+
+# Apply migrations
+python manage.py migrate
+```
+
+Always review the generated migration files before committing.
+
+### Authentication Patterns
+
+- Public endpoints use JWT tokens generated via `/initialize`
+- Private endpoints require authentication (check existing views for patterns)
+- Use the decorators in `app/decorators.py` for common auth patterns
+
+### Error Handling
+
+- Return appropriate HTTP status codes
+- Provide clear error messages in the response
+- Log errors for debugging
+- Follow the error handling patterns in existing views
+
+## Submitting Changes
+
+### 1. Push Your Branch
+
+```bash
+git push origin feature/your-feature-name
+```
+
+### 2. Create a Pull Request
+
+- Provide a clear title and description
+- Reference any related issues
+- Explain what changes were made and why
+- Include any testing steps
+
+### PR Description Template
+
+```markdown
+## Description
+Brief description of changes
+
+## Changes Made
+- List of specific changes
+- Another change
+
+## Testing
+How to test these changes
+
+## Related Issues
+Fixes #123
+```
+
+### 3. Code Review Process
+
+- A maintainer will review your PR
+- Address any feedback or requested changes
+- Once approved, your PR will be merged
+
+### CI/CD Checks
+
+Pull requests trigger automated workflows (see `.github/workflows/`):
+- Docker image builds
+- Code quality checks
+
+Ensure all checks pass before requesting review.
+
+## Getting Help
+
+- **Issues**: Report bugs or request features via [GitHub Issues](https://github.com/peermetrics/api-server/issues)
+- **Discussions**: Ask questions in the main [peermetrics repository](https://github.com/peermetrics/peermetrics)
+- **Documentation**: Check the [README](README.md) for project overview
+
+## Code Style
+
+- Follow PEP 8 guidelines for Python code
+- Use meaningful variable and function names
+- Keep line length reasonable (under 100 characters when possible)
+- Add docstrings to functions and classes
+
+## Additional Notes
+
+### Working with populate_db.py
+
+The `populate_db.py` script is useful for:
+- Generating realistic test data
+- Testing with different data volumes
+- Simulating various conference scenarios
+
+You can customize the test data by modifying files in `config_populate_db/`.
+
+### Database Tips
+
+- Use `python manage.py dbshell` to access the PostgreSQL shell
+- Run `python manage.py showmigrations` to see migration status
+- Use `python manage.py sqlmigrate app_name migration_name` to view SQL for a migration
+
+Thank you for contributing to peermetrics API server!