Add backpressure to incoming sync sessions
IncomingSession reads records from the transport as quickly as possible and queues them to be added to the DB. If the transport is faster than the DB, this will result in an unbounded number of records being queued. This uses an unbounded amount of memory, which is a DoS risk.
Add a backpressure mechanism that limits the amount of queued data and delays reading from the connection when the queue is full.