[FEATURE] Environment Variables Support for Configuration

[orenlab]

📋 Description

Implement comprehensive environment variable support for PyOutlineAPI configuration to improve deployment flexibility and security in production environments.

🎯 Objectives

• Add support for OUTLINE_API_URL environment variable
• Add support for OUTLINE_CERT_SHA256 for certificate configuration
• Implement secure credential management
• Add configuration validation with sensible defaults
• Create comprehensive documentation with examples

📝 Detailed Requirements

Environment Variables to Support:

OUTLINE_API_URL=https://your-outline-server.com
OUTLINE_CERT_SHA256=sha256fingerprint
OUTLINE_DEFAULT_TIMEOUT=30
OUTLINE_MAX_RETRIES=3
OUTLINE_LOG_LEVEL=INFO

Implementation Details:

• Use python-dotenv for .env file support
• Implement validation for URL formats and file paths
• Add fallback to hardcoded defaults
• Support both environment variables and programmatic configuration
• Ensure backward compatibility with existing configuration methods

🧪 Acceptance Criteria

• All configuration can be set via environment variables
• Configuration validation prevents invalid values
• Backward compatibility maintained
• Documentation includes setup examples
• Unit tests cover all configuration scenarios
• Integration tests with different environment setups

📚 Documentation Requirements

• Environment variable reference table
• Docker deployment examples
• Kubernetes ConfigMap examples
• Local development setup guide

🔗 Related Issues

• Will enable [FEATURE] Advanced Connection Management with Pooling and Recovery #8 (Connection Pooling configuration)
• Supports [FEATURE] Typed Exception System with Detailed Error Context #10 (Structured Logging configuration)

[orenlab]

Added in #12