Validate unknown=INCLUDE is not used in load_config()

This function also only deals with dataclasses as schemas, so that
option will never work.

Signed-off-by: Leandro Lucarella <[email protected]>

Author: llucax

RELEASE_NOTES.md

@@ -32,6 +32,7 @@ This release includes a new `ConfigManager` class to simplify managing the confi
 
          + The `base_schema` argument is now keyword-only and defaults to `BaseConfigSchema` (and because of this, it uses `unknown=EXCLUDE` by default).
          + The arguments forwarded to `marshmallow.Schema.load()` now must be passed explicitly via the `marshmallow_load_kwargs` argument, as a `dict`, to improve the type-checking.
+         + Will now raise a `ValueError` if `unknown` is set to `INCLUDE` in `marshmallow_load_kwargs`.
 
     * `ConfigManagingActor`: Raise a `ValueError` if the `config_files` argument an empty sequence.
 

src/frequenz/sdk/config/_util.py

@@ -72,6 +72,8 @@ def load_config(
     Returns:
         The loaded configuration as an instance of the configuration class.
     """
+    _validate_load_kwargs(marshmallow_load_kwargs)
+
     instance = class_schema(cls, base_schema)().load(
         config, **(marshmallow_load_kwargs or {})
     )