Function into_batch_commit_func 

pub fn into_batch_commit_func(commit: CommitFunc) -> BatchCommitFunc

Converts a CommitFunc into a BatchCommitFunc by wrapping it. This allows a function that commits a single message to be used where a function that commits a batch of messages is expected. It does so by extracting the first message from the response vector (if any) and passing it to the underlying single-message commit function.