Remove reflect from kafka update preview

[rkpattnaik780]

Description

The kafka update preview currently uses reflect package to parse data dynamically from updateObj struct. It depends largely on the SDK typings which can introduce breaking changes that could go undetected with the dynamic approach.

It can be simplified by operating directly on the SDK model properties.

Originally raised here.

[wtrocki]

Do you want me to see if backend can fix it?

[craicoverflow]

This is not something the backend can fix.

[wtrocki]

Ok. I got impression that defining object in openapi will fix it