Created middleware to keep backwards compatibility on errors when using v1 and 2 of the API

module/Rest/src/Middleware/ErrorHandler/BackwardsCompatibleProblemDetailsHandler.php

@@ -0,0 +1,30 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Shlinkio\Shlink\Rest\Middleware\ErrorHandler;
+
+use Mezzio\ProblemDetails\Exception\ProblemDetailsExceptionInterface;
+use Psr\Http\Message\ResponseInterface;
+use Psr\Http\Message\ServerRequestInterface;
+use Psr\Http\Server\MiddlewareInterface;
+use Psr\Http\Server\RequestHandlerInterface;
+use Shlinkio\Shlink\Rest\Exception\BackwardsCompatibleProblemDetailsException;
+
+use function version_compare;
+
+/** @deprecated */
+class BackwardsCompatibleProblemDetailsHandler implements MiddlewareInterface
+{
+    public function process(ServerRequestInterface $request, RequestHandlerInterface $handler): ResponseInterface
+    {
+        try {
+            return $handler->handle($request);
+        } catch (ProblemDetailsExceptionInterface $e) {
+            $version = $request->getAttribute('version') ?? '2';
+            throw version_compare($version, '3', '>=')
+                ? $e
+                : BackwardsCompatibleProblemDetailsException::fromProblemDetails($e);
+        }
+    }
+}