* we used to notify ourselves on BOOST IT, now we tend to get
  notifications on `DIAGNOSTICS`. let's be consistent about that!
* while at it: send these notifications in sequence. if a big channel
  is destroyed or recycled, we don't want signald to shit the bed
* aaaand... let's make `_notifyMany` handle either a concrete message
  or a notification key so we can use it as a helper for all of our
  notify functions