private static SignerProvider createSignerProvider(String region) {
        AWS4Signer signer = new AWS4Signer();
        signer.setRegionName(assertStringNotEmpty(region, "region"));
        signer.setServiceName(SERVICE_NAME);
        return new StaticSignerProvider(signer);
    }
@param credentialsProvider Credentials to use to sign the auth token.
@param region              Region the database is located in.
aws-java-sdk-rds/src/main/java/com/amazonaws/services/rds/auth/RdsIamAuthTokenGenerator.java