support periodic manual commits

[jsvd]

A manual periodic commit could be called manual_commit_interval_ms, where (if enable_auto_commit is false):

• = 0 (default): commits on every poll
• > 0: commits offsets at every interval (approximately)

This check would be done before the poll call (or after writing to the queue), so the interplay between poll_timeout_ms, fetch_max_wait_ms, request_timeout_ms and this new manual_commit_interval_ms would have to be sanity checked to ensure the users sets sane values.

for more context please see: #267 (comment)

[maverick298]

+1

[DeeeFOX]

+1

[DeeeFOX]

amazing for this issue is still opening, and may last for years...