Improve API error handling

- Change 'path' key to 'source.pointer', as per spec
- Add 500 error detail if debug mode is on

src/Api/Client.php

@@ -12,6 +12,8 @@ namespace Flarum\Api;
 
 use Flarum\Core\Users\User;
 use Illuminate\Contracts\Container\Container;
+use Exception;
+use Flarum\Api\Middleware\JsonApiErrors;
 
 class Client
 {
@@ -41,7 +43,13 @@ class Client
         /** @var \Flarum\Api\Actions\Action $action */
         $action = $this->container->make($actionClass);
 
-        $response = $action->handle(new Request($input, $actor));
+        try {
+            $response = $action->handle(new Request($input, $actor));
+        } catch (Exception $e) {
+            $middleware = new JsonApiErrors();
+
+            $response = $middleware->handle($e);
+        }
 
         return new Response($response);
     }