JStructuredLogger class

Structured logger that outputs JSON-formatted log messages.

This logger provides:

• Structured JSON output for easier parsing and analysis
• Log levels (trace, debug, info, warn, error)
• Timestamps for all log entries
• Context propagation through correlation IDs
• PII handling guidance (user must redact sensitive data)

Example usage:

void main() {
  final logger = JStructuredLogger(
    minLevel: LogLevel.info,
    serviceName: 'my-app',
  );

  logger.info('User logged in', context: {
    'userId': '12345',
    'correlationId': 'abc-123',
  });
}