They will be described in the release notes, but gist:

Added:
- `DeliverSubject()` option to configure the deliver subject of a JetStream consumer created by the `js.Subscribe()` call (and variants)
- `BindDeliverSubject()` option to subscribe directly to a JetStream consumer deliver subject (bypassing any lookup or JetStream consumer creation)
- Fields `DeliverGroup` in `ConsumerConfig`, `PushBound` in `ConsumerInfo`. They help making prevent incorrect subscriptions to JetStream consumers
- Field `Last` in `SequencePair`

Changed:
- With a `PullSubscription`, calling `NextMsg()` or `NextMsgWithContext()` will now return `ErrTypeSubscription`. You must use the `Fetch()` API
- If the library created internally a JetStream consumer, the consumer will be deleted on `Unsubscribe()` or when the `Drain()` completes
- Fail multiple instances of a subscription on the same durable push consumer (only one active at a time). Also, consumers now have the concept of `DeliverGroup`, which is the queue group name they are created for. Only queue member from the same group can attach to this consumer, and a non queue subscription cannot attach to it. Note that this requires server v2.3.5
- Attempting to create a queue subscription with a consumer configuration that has idle heartbeats and/or flow control will now result in an error

Fixed:
- Possible lock inversion
- JetStream consumers could be incorrectly deleted on subscription's `Unsubscribe()`

Resolves nats-io#785
Resolves nats-io#776
Resolves nats-io#775
Resolves nats-io#748
Resolves nats-io#747

Signed-off-by: Ivan Kozlovic <ivan@synadia.com>