Add a new buffered_sub_entry_messages in Producer

[garvenlee]

The messages in send and send_sub_entry can be handled separately in the _timer task like this:

async def _timer(self):
    while True:
        await sleep(delay)
        for stream, messages in buffered_messages.items():
            await _send_batch()

        for stream, messages in buffered_sub_entry_messages.items():
            await _send_sub_entry_batch()

And redesign the _send_batch: the arg sync is only used in function send_wait, so it can be removed from _send_batch.

[Gsantomaggio]

Thank you, feel free to open a PR !

[DanielePalaia]

Ah yes this is also a known issue: #55

There was a plan to redesign it but with lower priority.

But yes feel free to open a PR!

[DanielePalaia]

I take this issue also to decouple send_batch from send/send_sub_batch in order to avoid the initial loop:
See: #148

[DanielePalaia]

I will close this issue as it is not a top priority at the moment.
We already made some decouples of the API in the past here:
#55

At the moment even if it's possible to run the client in parallel on the two different modes: normal, and with sub-entry-batch enabled I don't think it will really be a common case so at the moment we will focus on other improvements.

We will come back to it in a next iteration if needed