Subscribe in reverse chronological order

[cruickshankpg]

We have a use case to subscribe to a stream in reverse chronological order from an offset/timestamp. To achieve this on the consumer side we'd need to do lots of in memory caching or multiple requests so ideally Liftbridge could do it for us.

I would plan on it being exposed as a new reverse bool on the SubscribeRequest and a SubscriptionOption in the client library.

Also I think being able to get reverse order would help make cursor fetching more efficient:

liftbridge/server/cursors.go

Line 193 in 383469b

func (c *cursorManager) getLatestCursorOffset(ctx context.Context, cursorKey []byte, partitionID int32) (int64, error) {

I'm happy to have a go at implementing this.

[tylertreat]

Go for it. I thought the same thing when implementing cursor fetching.