Question about filters and CORS

[Leviathan856]

Hi,
I have encountered some troubles implementing custom filters to enable access to server from a front-end application.
So, I added the following code and couldn't figure out why the custom filter is not applied (doFilter function was not called):

class AuthFilter : public drogon::HttpFilter<AuthFilter, false>
{
public:
    void doFilter(const drogon::HttpRequestPtr &req,
                        drogon::FilterCallback &&fcb,
                        drogon::FilterChainCallback &&fccb) override
    {
        auto resp = drogon::HttpResponse::newHttpResponse();

        resp->addHeader("Access-Control-Allow-Origin", "http://localhost:xxxx");

        fcb(resp);
    }
};

int main()
{
    auto authFilter = std::make_shared<AuthFilter>();

    app()
        .loadConfigFile("./config.json")
        .setLogPath("./build/log")
        .registerFilter(authFilter)
        .registerBeginningAdvice(serviceSetup)
        .run();
    return EXIT_SUCCESS;
}

static void serviceSetup()
{
...
    app()
        .registerHandler("/api/auth/isUserExist?username={username}", &usernameCheck, {Get, "AuthFilter"})
        .registerHandler("/api/auth/signup", &signUpHandler, {Post, "AuthFilter"})
        .registerHandler("/api/auth/signin", &signInHandler, {Post, "AuthFilter"});
...
}

I know I can bypass using filters by using registerPostHandlingAdvice, but I need different policy for different controllers.
I would appreciate any help on this issue