Persistent subscriptions next-gen

Seems like persistent subscriptions aim to solve two problems:

• Server-side checkpointing for use cases when events are being forwarded to a place that doesn't have the ability to store checkpoints (message brokers), or users just don't want to deal with checkpoints.

• High availability of subscribers (consumers)

Each of those cases can be solved separately. It might be a good idea to allow HA for consumers using the Connector, and also use server-side checkpointing provided by Connector.