Enhance WritingHandler flexibility and error reporting

[ZivoMartin]

The current WritingHandler waits for all senders to finish their writing when calling the wait method. While this is generally effective, there are scenarios where users may need more fine-grained control

Proposed Enhancements:
Selective Waiting for Specific Senders:

• Provide a method to specify which senders (by their IDs) should be awaited.
• This allows users to track the progress of specific senders rather than waiting for all of them.
  Error Reporting with Sender Identification:
• Currently, when a sender fails, the error returned does not indicate which sender caused the failure.
• Add an enhancement to include sender IDs in the error reporting, so users know which sender failed.
  While this adds value, it may not be a high-priority enhancement as many use cases do not require per-sender control.