refactoring: remove content from `CommandResult`

# Feature Request

> there will be a subsequent refactoring to remove the `CommandResult` content as it was introduced in #5576 to get the job done, but actually the information that's needed by the service layer (entity id and createdAt) are already available there, and the command should stay without content, for sake of simplicity

(ref. #5579 )

## Which Areas Would Be Affected?

_e.g., DPF, CI, build, transfer, etc._

## Why Is the Feature Desired?

_Are there any requirements?_

## Who will sponsor this feature?

_Please @-mention the committer that will sponsor your feature_.

## Solution Proposal

_If possible, provide a (brief!) solution proposal._