[Jon to write schema]
EventLogging should be wired up to measure impact of engagement.
* Enable EventLogging on a 1% sample of users using read more (note read more is in beta so this will be 1% of users in beta).
* Sample rate will be configurable by global config variable. We will tweak it as we go.
* Send an event when the Read More section is first scrolled into view.
* If the user taps one of the items inside read more, send an event with the index of the item that was tapped.
* It should be possible to link the above two events to answer "if user saw read more what % engaged with it"
* We hope that ~~12.5~~ 5% of visits that see read more, engage with read more. (In apps we saw 12.5% but we expect them to be a more engaged audience)
* Events should include a unique user session id, whether they were generated by api or magic word