default String getJsonWebKeySigningAlgorithm(final OAuthRegisteredService registeredService,
                                                 final JsonWebKey signingKey) {
        var defaultAlgorithm = AlgorithmIdentifiers.RSA_USING_SHA256;
        if (signingKey instanceof EllipticCurveJsonWebKey) {
            defaultAlgorithm = AlgorithmIdentifiers.ECDSA_USING_P256_CURVE_AND_SHA256;
        }
        return StringUtils.defaultIfBlank(signingKey.getAlgorithm(), defaultAlgorithm);
    }
Gets json web key signing algorithm.

@param registeredService        the svc
@param signingKey the signing key
@return the json web key signing algorithm
support/cas-server-support-oauth-core-api/src/main/java/org/apereo/cas/ticket/OAuth20TokenSigningAndEncryptionService.java