[Feature Request] Support PutUserProperty

In java we can use `message. putUserProperty` to append some metadata into message, this is sometimes very useful, but in nodejs client we have not found how we can do this. Could you support this please?

Start by locating the Node.js client's message API and compare its available metadata methods with Java's message.putUserProperty behavior. Implement the equivalent user-property capability in the client and verify that callers can append metadata to messages.

Written by the indexing model from the issue text.