tests: add IndexController tests

config/services_test.yaml

@@ -0,0 +1,12 @@
+services:
+  # default configuration for services in *this* file
+  _defaults:
+    autowire: true      # Automatically injects dependencies in your services.
+    autoconfigure: true # Automatically registers your services as commands, event subscribers, etc.
+    public: true
+
+  App\Service\QRCodeGeneratorInterface:
+    lazy: true
+    public: true
+  # add more service definitions when explicit configuration is needed
+  # please note that last definitions always *replace* previous ones