default Collection<SingleLogoutUrl> determineLogoutUrl(final RegisteredService registeredService,
                                                           final WebApplicationService singleLogoutService) {
        return determineLogoutUrl(registeredService, singleLogoutService, Optional.empty());
    }
Determine logout url collection.

@param registeredService   the registered service
@param singleLogoutService the single logout service
@return the collection
api/cas-server-core-api-logout/src/main/java/org/apereo/cas/logout/slo/SingleLogoutServiceLogoutUrlBuilder.java