public Builder withIdentityProvider(ServiceIdentityProvider identityProvider) {
            this.sslContextSupplier = identityProvider::getIdentitySslContext;
            return this;
        }
Default implementation of {@link ZtsClient}

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