Add docs and example

Author: rmk135

docs/providers/configuration.rst

@@ -72,6 +72,20 @@ where ``examples/providers/configuration/config.yml`` is:
 .. literalinclude:: ../../examples/providers/configuration/config.yml
    :language: ini
 
+Alternatively, you can provide a path to the YAML file over the configuration provider argument. In that case,
+the container will call ``config.from_yaml()`` automatically:
+
+.. code-block:: python
+   :emphasize-lines: 3
+
+   class Container(containers.DeclarativeContainer):
+
+       config = providers.Configuration(yaml_files=["./config.yml"])
+
+
+   if __name__ == "__main__":
+       container = Container()  # Config is loaded from ./config.yml
+
 :py:meth:`Configuration.from_yaml` method supports environment variables interpolation.
 
 .. code-block:: ini

examples/providers/configuration/configuration_yaml_init.py

@@ -0,0 +1,25 @@
+"""`Configuration` provider values loading example."""
+
+from dependency_injector import containers, providers
+
+
+class Container(containers.DeclarativeContainer):
+
+    config = providers.Configuration(yaml_files=["./config.yml"])
+
+
+if __name__ == "__main__":
+    container = Container()
+
+    assert container.config() == {
+        "aws": {
+            "access_key_id": "KEY",
+            "secret_access_key": "SECRET",
+        },
+    }
+    assert container.config.aws() == {
+        "access_key_id": "KEY",
+        "secret_access_key": "SECRET",
+    }
+    assert container.config.aws.access_key_id() == "KEY"
+    assert container.config.aws.secret_access_key() == "SECRET"