R1:42c0f060d5d0

Push feed publishing deeper into the task queue

Summary:
Ref T2852. I want to model Asana integration as a response to feed events. Currently, we queue one feed event for each HTTP hook.

Instead, always queue one feed event and then have it queue any necessary followup events (now, http hooks; soon, asana).

Add a script to make it easy to reproducibly fire feed event publishing.

Test Plan:
Republished a feed event and verified it hit configured HTTP hooks correctly.

$ ./bin/feed republish…