This adds raft-based quorum queues and mixed cluster version upgrades.
Package builds, upgraded a single node & checked web ui & rabbitmq-diagnostics
"Works on My Machine"
I can't test a multi-node upgrade but otherwise it seems fine.
I would wait for 3.8.1 (and skip 3.7.18): there is a bug with cluster upgrades in 3.7.18 and 3.8.0 when files are overwritten while the service is still running (because new modules are available in an old node).
Felix Ehlers on Twitter found out that setting RABBITMQ_SERVER_ADDITIONAL_ERL_ARGS="+sbwt none" seems to reduce CPU usage.
What do you think? Could it be worthwhile to integrate it somehow, maybe as an setting in rc.conf?