private static Map<String, String> getClaimMappingsContainer(final RegisteredService registeredService) {
        var finalMap = Stream.<Map.Entry<String, String>>empty();
        if (registeredService.getAttributeReleasePolicy() instanceof final RegisteredServiceChainingAttributeReleasePolicy chain) {
            for (val policy : chain.getPolicies()) {
                val result = getClaimMappingsForPolicy(policy);
                finalMap = Stream.concat(finalMap, result);
            }
        }
        val result = getClaimMappingsForPolicy(registeredService.getAttributeReleasePolicy());
        val finalResult = Stream.concat(finalMap, result);
        return finalResult.collect(Collectors.toMap(Map.Entry::getKey, Map.Entry::getValue));
    }
Map OIDC claim to an attribute.
support/cas-server-support-oidc-core-api/src/main/java/org/apereo/cas/oidc/claims/OidcDefaultAttributeToScopeClaimMapper.java