I hope the comments explain the changes. `notifyWorkers` notifies a worker which then calls `processServer`, which in turn gets all users and calls `processServerUser`. There is no need to call `processServer` for the same domain on startup.
Sister PR to https://github.com/matrix-org/gomatrixserverlib/pull/364 Read this commit by commit to avoid going insane.
Part of a series of refactors on GMSL.
As discussed yesterday, a first draft of merging the keyserver and the userapi.
