After registration, login and redirect user to custom page

wp_user_register_redirect

/**
 * After registrartion, login and redirect user to a custom page
 */
 
function auto_login_registration_redirect() {
  // Login the user automatically
	$user_login = $_POST['user_login'];
	$user = get_userdatabylogin($user_login);
	$user_id = $user->ID;
	wp_set_current_user($user_id, $user_login);
	wp_set_auth_cookie($user_id);
	do_action('wp_login', $user_login);

	// Redirect somewhere
	wp_redirect( home_url( '/registration-complete-thanks/' ) );
	exit();
}
add_action( 'user_register', 'auto_login_registration_redirect' );