Use db-config pre-seeding to handle database updates

[abmargb]

Although our deb packages support db-config, right now we don't use it in the Dockerfiles. We simply install the packages with a fake connection info and then stage the proper configuration.

Having db-config pre-seeding in place will make DB upgrades a lot smoother.

[abmargb]

See https://github.com/buddycloud/dockerfiles/blob/master/buddycloud-stack/Dockerfile#L47

[imaginator]

What about having the server startup and apply any new versions to the DB automatically? I generally don't like this servers changing database schemas behind the admin's back ([schema upgrade starts]"Why is this taking so long to startup? I'm going to restart again. And again" leading to db corruption.)

I guess wrapping the entire upgrade in a transaction could help. Either way, I think it's dangerous to have a new version of a server roll a schema forward. Then if something doesn't work, there's no easy rollback.

I'll have another coffee and think about this more.