Improve ease of extention

In our usage we need to extend the ControllerInvoker to have responses
normalised from a generic Payload into a standard Response.

To make this easier it would be helpful if some private methods were
instead protected and the Invoker fetching the default resolver chain
were separated out from the creation of the ControllerInvoker.

Fixes #105

src/Bridge.php

@@ -39,7 +39,10 @@ public static function create(?ContainerInterface $container = null): App
         return $app;
     }
 
-    private static function createControllerInvoker(ContainerInterface $container): ControllerInvoker
+    /**
+     * Create an invoker with the default resolvers.
+     */
+    protected static function createInvoker(ContainerInterface $container): Invoker
     {
         $resolvers = [
             // Inject parameters by name first
@@ -50,8 +53,14 @@ private static function createControllerInvoker(ContainerInterface $container):
             new DefaultValueResolver,
         ];
 
-        $invoker = new Invoker(new ResolverChain($resolvers), $container);
+        return new Invoker(new ResolverChain($resolvers), $container);
+    }
 
-        return new ControllerInvoker($invoker);
+    /**
+     * Create a controller invoker with the default resolvers.
+     */
+    protected static function createControllerInvoker(ContainerInterface $container): ControllerInvoker
+    {
+        return new ControllerInvoker(self::createInvoker($container));
     }
 }

src/ControllerInvoker.php

@@ -24,7 +24,6 @@ public function __construct(InvokerInterface $invoker)
      * @param ServerRequestInterface $request        The request object.
      * @param ResponseInterface      $response       The response object.
      * @param array                  $routeArguments The route's placeholder arguments
-     * @return ResponseInterface|string The response from the callable.
      */
     public function __invoke(
         callable $callable,
@@ -42,10 +41,26 @@ public function __invoke(
         // Inject the attributes defined on the request
         $parameters += $request->getAttributes();
 
-        return $this->invoker->call($callable, $parameters);
+        return $this->processResponse($this->invoker->call($callable, $parameters));
     }
 
-    private static function injectRouteArguments(ServerRequestInterface $request, array $routeArguments): ServerRequestInterface
+    /**
+     * Allow for child classes to process the response.
+     *
+     * @param ResponseInterface|string $response The response from the callable.
+     * @return ResponseInterface|string The processed response
+     */
+    protected function processResponse($response)
+    {
+        return $response;
+    }
+
+    /**
+     * Inject route arguments into the request.
+     *
+     * @param array                  $routeArguments
+     */
+    protected static function injectRouteArguments(ServerRequestInterface $request, array $routeArguments): ServerRequestInterface
     {
         $requestWithArgs = $request;
         foreach ($routeArguments as $key => $value) {