Swapping middlewares handler

Most of the things that come with Glue are easily swappable as they're simply service providers you can or not include. The PSR7 middlewares handlers (Relay by default) is however more ingrained into Glue, you can still easily change it though by changing the pipeline binding on the container.

It simply has to return a callable accepting a request and response, and returning a response. So it can be a closure, or any class with an __invoke magic method:

// With a closure
$container = new Container();
$container->share('pipeline', function() {
    return function ($request, $response) {
        // Process my request and response here
    };
});

// With a class implementing __invoke
$container = new Container();
$container->share('pipeline', function() {
    $pipe = new MyMiddlewareHandler();

    $middlewares = $this->container->get('config.middlewares');
    foreach ($middlewares as $middleware) {
        $pipe->pipe($middleware);
    }

    return $pipe;
});

$app = new Glue();
$app->setContainer($container);