public DefaultZtsClient build() {
            if (sslContextSupplier == null)
                throw new IllegalArgumentException("No SSL context or identity provider available to set up ZTS client");
            return new DefaultZtsClient(ztsUrl, sslContextSupplier, hostnameVerifier, errorHandler);
        }
Default implementation of {@link ZtsClient}

@author bjorncs
@author mortent
vespa-athenz/src/main/java/com/yahoo/vespa/athenz/client/zts/DefaultZtsClient.java