Create URL generator interface.

Also bind a default implementation to the container.

src/Http/UrlGenerator.php

@@ -0,0 +1,28 @@
+<?php
+
+namespace Flarum\Http;
+
+class UrlGenerator implements UrlGeneratorInterface
+{
+    protected $router;
+
+
+    public function __construct(Router $router)
+    {
+        $this->router = $router;
+    }
+
+    public function toRoute($name, $parameters = [])
+    {
+        $path = $this->router->getPath($name, $parameters);
+        $path = ltrim($path, '/');
+
+        // TODO: Prepend real base URL
+        return "/$path";
+    }
+
+    public function toAsset($path)
+    {
+        return "/$path";
+    }
+}