addMap method
Adds a generic Map<String, dynamic> provider.
Nested maps are flattened using colon-separated keys:
{'database': {'host': 'localhost'}} → {'database:host': 'localhost'}.
Non-string leaf values are converted with .toString().
Implementation
ConfigurationBuilder addMap(Map<String, dynamic> map) {
_sources.add(MapConfigurationSource(map: map));
return this;
}