Allow the response in send_block_request_message to be customized

[coderabbitai]

There is a need to allow customization of the response status and body when blocking. Currently, the response status code and message are hardcoded, which might not be suitable for all contexts. This change would allow the response to be more dynamic and adaptable to different scenarios, enhancing the flexibility of the error handling.

For more details, see the discussion here: #342 (comment)

[sporkmonger]

This is essentially a duplicate of #144.