Which use case/requirement will be addressed by the proposed feature?

Deploying a debezium server instance with a pre-created, custom named SA provided by the user.

Details:
Currently it is not possible to use a SA named differently than the predefined one ('<DebeziumServer instance name>-sa').

Additionally, it is not possible to use a pre-created SA for the debezium server instance, because in such case the operator fails with the message:
"Operation cannot be fulfilled on serviceaccounts "<SA name>": the object has been modified".

To be clear, it is currently possible to grant additional RBACs/other IAMs to the SA sued by the debezium server (you just apply the changes after creating the DbzServer and use the predefined name), but I think this will be a small change and a significant improvement for managed k8s clusters being run on public clouds.