Snapshot Event Handler State

[marpo60]

Context

Event Handler State is provided in the init/1 callback and can be updated in each handle/2
https://hexdocs.pm/commanded/1.3.0/Commanded.Event.Handler.html#module-event-handler-state

This is pretty handy, but at this moment the state is ephemeral, which means that on server restart, there is a need to reconstruct the state.

It would be awesome if the EventHandler state could be persisted in the same fashion as the Process Manager state.

commanded/lib/commanded/process_managers/process_manager_instance.ex

Lines 82 to 84 in 1c8af07

	def init(%State{} = state) do
	{:ok, state, {:continue, :fetch_state}}
	end

commanded/lib/commanded/process_managers/process_manager_instance.ex

Line 243 in 1c8af07

:ok = persist_state(event_number, state)

If there is value in doing this I can start implementing this.

[slashdotdash]

Yes, I agree this would be a useful opt-in feature for event handlers. A pull request would be very welcome, thanks!