Some way to drain the message queue

[bruno]

In some situations it can be useful to flush all the remaining entries in the message queue.

For example, suppose you had an index put in 'subscribe do not listen' state, and afterwards you want to re-enable the index but you realize you don't want all those outstanding events to be processed.

As a workaround, for the case of indexing, you could do something like set an empty indexer conf, so that no actual indexing work is performed, but that's still far from optimal (messages still delivered to indexer, which will read payload and will read each record to find out its type.

You could also just drop the index, which would drop its subscription, but there's no actual cleanup procedure there either.