protected List<Service> collectServicesToMatch(final RequestContext context, final String ticketGrantingTicketId) {
        val ticket = StringUtils.isNotBlank(ticketGrantingTicketId)
            ? ticketRegistrySupport.getTicketGrantingTicket(ticketGrantingTicketId)
            : null;
        return ticket != null ? new ArrayList<>(ticket.getServices().values()) : new ArrayList<>();
    }
Configure webflow for initial mandatory service.

@param context                the context
@param ticketGrantingTicketId the ticket granting ticket id
@param initialServicePattern  the initial service pattern
support/cas-server-support-actions-core/src/main/java/org/apereo/cas/web/flow/login/VerifyRequiredServiceAction.java