example: Add example of user authencate l2 switch like an AP on cafe

examples/cafe/config/config.exs

@@ -0,0 +1,20 @@
+# This file is responsible for configuring your application
+# and its dependencies with the aid of the Mix.Config module.
+use Mix.Config
+
+# By default, the umbrella project as well as each child
+# application will require this configuration file, as
+# configuration and dependencies are shared in an umbrella
+# project. While one could configure all applications here,
+# we prefer to keep the configuration of each individual
+# child application in their own app, but all other
+# dependencies, regardless if they belong to one or multiple
+# apps, should be configured in the umbrella to avoid confusion.
+import_config "../apps/*/config/config.exs"
+
+# Sample configuration (overrides the imported configuration above):
+#
+#     config :logger, :console,
+#       level: :info,
+#       format: "$date $time [$level] $metadata$message\n",
+#       metadata: [:user_id]