Allow setting Annotations and MessageHeaders

[hae-andrew-young]

Is your feature request related to a problem? Please describe.

These are internal properties at the moment and we would like to be able to set them to put metadata about the payload in there.

Describe the solution you'd like

see above.

Describe alternatives you've considered

We could set them in ApplicationProperties. Would that be the right approach for this?

Additional context

No response

[Gsantomaggio]

Hi @hae-anyoung
Please have a look on: https://www.rabbitmq.com/docs/stream-core-plugin-comparison#interoperabilty

The fieldsAnnotations and MessageHeaders are only for compatibility. This is why the fields are in readonly !

You can use ApplicationProperties to set the information you need.