This was once mentioned in the PR #1537 and I think it would make sense to do so.

The idea is to add a messaging-service (setting) called auto that acts like currently none does.
none is a bit misleading since it technically isn't just none. It acts as sql when you use MySQL or MariaDB as database and can cause problems if people don't want to have a messaging service set.
The setting none should always do nothing or else it just becomes confusing.

So add the auto option as new default, which would do act as sql when using MySQL/MariaDB and else nothing (is disabled).
And when we would make none to actually disable the service, then let us get rid of notsql since it wouldn't be used anymore with this new configuration.

This would be a good change for v5, since that'll break lots of other stuff too.

Added in v5 - thanks :)