Support for Metadata in message

[Gaurav-CareMonitor]

Is your feature request related to a problem? Please describe.
We need support for adding metadata in message class to use it in custom builder.

[aditya-css]

Hi @Gaurav-CareMonitor,
This seems a reasonable request and fairly straightforward to implement as well. We would appreciate contribution from your end if you are up for it.

The Message class is moved to chatview_utils package so you can create a PR there and add a metadata field of type Map.

Let me know if you would not get time to make this change or need any help or further clarifications in case you choose to contribute. Happy coding.