Event to action. An automation is a trigger and a graph: something happens,
and a run walks the steps for the subscriber it happened to, sending,
waiting, moving tags and branching on a condition. Needs sending, because
what an automation decides is that the list will receive something.
Every event Commune publishes is a trigger. GET /automation-triggers says
which are about a subscriber and what each one's events carry, which is what
a condition can ask about.
Nothing an automation holds reaches anybody until it is turned on, which is one operation of its own with every gate behind it.