Add custom REST endpoints in keycloak

I'm creating custom endpoints following the documentation

But I have version problems.

• In the development of custom endpoints I'm using the 12.0.4 version of keycloak.
• In production the keycloak is in version 11.0.3

In version 12.0.4 I can verify authentication this way:

...

public KeyCloakUserApiProvider(KeycloakSession session) {
    this.session = session;
    this.auth = new AppAuthManager.BearerTokenAuthenticator(session).authenticate();
}

...

public static void checkRealmAdmin(AuthenticationManager.AuthResult auth) {
    if (auth == null || auth.getSession() == null || auth.getSession().getUser() == null) {
        throw new ForbiddenException("User not authenticated");
    } else {
        boolean isAdmin = auth.getSession()
                .getUser()
                .getRoleMappingsStream()
                .anyMatch(r-> r.getName().equals("ADMINISTRATOR") || r.getName().equals("ADMIN"));
        if (!isAdmin) {
            throw new ForbiddenException("User is not admin");
        }
    }
}

But in version 11.0.3 there is no such method:

new AppAuthManager.BearerTokenAuthenticator(

Can I do this authentication check in what way in version 11.0.3?