Allow a subscription to set a batch size and time interval

[tillrohrmann]

A user requested the following feature: Allow a subscription to set a batch size and time interval. The time interval used to poll Kafka and the buffer size the max number of records to send in one message to the subscribing service. This will make the service more efficient than one at a time messaging.

[1] https://discord.com/channels/1128210118216007792/1136316066696532069/1183605557190459574