in grpc-web/callout/src/main/java/com/google/apigee/callouts/ProtobufDecoder.java [61:64]
private void saveOutputs(MessageContext msgCtx, ByteArrayOutputStream stdoutOS, ByteArrayOutputStream stderrOS) {
msgCtx.setVariable("pb-decoder.info.stdout", new String(stdoutOS.toByteArray(), StandardCharsets.UTF_8));
msgCtx.setVariable("pb-decoder.info.stderr", new String(stderrOS.toByteArray(), StandardCharsets.UTF_8));
}