@Override
    @JsonIgnore
    public Collection<String> getAllowedProviders() {
        return strategies.stream()
            .map(RegisteredServiceDelegatedAuthenticationPolicy::getAllowedProviders)
            .flatMap(Collection::stream)
            .collect(Collectors.toSet());
    }
Add policy/strategy.

@param policy the provider
core/cas-server-core-services-api/src/main/java/org/apereo/cas/services/ChainingRegisteredServiceDelegatedAuthenticationPolicy.java