PropertiesPropertySource constructor

A specialized MapPropertySource that represents traditional Java-style .properties-like configuration, Dart-style .dart-like configuration, Environment .env-like configuration, and YAML-style .yaml-like configuration as a Dart Map.

It provides semantic clarity when you're loading configurations from a .properties file or equivalent structured source, and is typically used in environments where key-value pairs are treated as flat string mappings.

This class does not add new behavior to MapPropertySource, but helps clearly differentiate the source of configuration in a MutablePropertySources stack.

Example usage:

final props = {
  'server.port': '8080',
  'logging.level': 'INFO',
};

final propertySource = PropertiesPropertySource('application.properties', props);

print(propertySource.getProperty('server.port')); // 8080

This can be combined with other sources for layered configuration.