Replace request-id middleware dependency with userland code

module/Rest/test-api/Middleware/RequestIdTest.php

@@ -0,0 +1,30 @@
+<?php
+
+declare(strict_types=1);
+
+namespace ShlinkioApiTest\Shlink\Rest\Middleware;
+
+use GuzzleHttp\RequestOptions;
+use PHPUnit\Framework\Attributes\Test;
+use Shlinkio\Shlink\TestUtils\ApiTest\ApiTestCase;
+
+class RequestIdTest extends ApiTestCase
+{
+    #[Test]
+    public function generatesRequestId(): void
+    {
+        $response = $this->callApi('GET', '/health');
+        self::assertTrue($response->hasHeader('X-Request-Id'));
+    }
+
+    #[Test]
+    public function keepsProvidedRequestId(): void
+    {
+        $response = $this->callApi('GET', '/health', [
+            RequestOptions::HEADERS => [
+                'X-Request-Id' => 'foobar',
+            ],
+        ]);
+        self::assertEquals('foobar', $response->hasHeader('X-Request-Id'));
+    }
+}