default AwsTemporaryCredentials getAwsTemporaryCredentials(AthenzDomain athenzDomain, AwsRole awsRole, String externalId) {
        return getAwsTemporaryCredentials(athenzDomain, awsRole, null, externalId);
    }
Get AWS temporary credentials

@param awsRole AWS role to get credentials for
@param externalId External Id to get credentials, or <code>null</code> if not required
@return AWS temporary credentials
vespa-athenz/src/main/java/com/yahoo/vespa/athenz/client/zts/ZtsClient.java