@Override
    public Resource resolveSigningKey(final Optional<SamlRegisteredService> registeredService) throws Throwable {
        return getMetadataArtifact(registeredService, "idp-signing.key");
    }
This is {@link FileSystemSamlIdPMetadataLocator}.

@author Misagh Moayyed
@since 5.3.0
support/cas-server-support-saml-idp-core/src/main/java/org/apereo/cas/support/saml/idp/metadata/locator/FileSystemSamlIdPMetadataLocator.java