RequestServer: Make Request::url() virtual

Let the Request subclass decide how they store the URL instead of
storing it in a Request member.

Userland/Services/RequestServer/HttpsRequest.h

@@ -21,6 +21,8 @@ public:
     HTTP::HttpsJob& job() { return m_job; }
     HTTP::HttpsJob const& job() const { return m_job; }
 
+    virtual URL url() const override { return m_job->url(); }
+
 private:
     explicit HttpsRequest(ClientConnection&, NonnullRefPtr<HTTP::HttpsJob>, NonnullOwnPtr<OutputFileStream>&&);