WIP: Add support to subscribe to sub-keys

Author: llucax

src/frequenz/sdk/config/__init__.py

@@ -65,6 +65,10 @@ async def main() -> None:
     ```
 """
 
+# TODO:
+# This still needs support to filter by sub-keys using the dot
+# notation (so "key.subkey" should subscribe to config["key"]["subkey"]
+
 from ._actor import ConfigManagingActor
 from ._global import config_manager, initialize_config, shutdown_config_manager
 from ._logging_actor import LoggerConfig, LoggingConfig, LoggingConfigUpdatingActor