SystemEnvironmentPropertySource constructor

A MapPropertySource that exposes system environment variables as a property source.

This class wraps a Map<String, String> of environment variables, typically obtained from Platform.environment, and exposes it through the property resolution system.

This allows the environment to be queried like any other configuration source, with consistent property access patterns.

Example usage:

import 'dart:io';

final envSource = SystemEnvironmentPropertySource('systemEnv', Platform.environment);

print(envSource.getProperty('HOME')); // e.g. /Users/yourname
print(envSource.containsProperty('PATH')); // true

Can be added to a MutablePropertySources stack for prioritized resolution.

final sources = MutablePropertySources();
sources.addLast(envSource);