refs https://github.com/TryGhost/Team/issues/469
In order to reduce noise, we want to only display newsletter
subscription events which are not likely to be the result of a member
signup. The approach we've taken is to remove any newsletter
subscription (not unsubscription) event, if when sorted in chronological
order, it is to reside next to a signup event for the same member.
An improvement to this approach might be to add some kind of transaction
id to events which would allow us to group together events which should
be considered to have happened simultaneously.
refs https://github.com/TryGhost/Team/issues/469
Signup events are captured by status changes with no `from_status`, this
means that the member did not have a status (did not exist) before this
change.
refs https://github.com/TryGhost/Team/issues/469
We order the set of all events by created_at, but were not fetching the
individual events with the same order applies, this resulted in
incorrect results.
refs https://github.com/TryGhost/Ghost/issues/12602
* Added Event Repository
** Added method for MRR over time
** Added method for newsletter subscriptions over time
** Added method for gross volume over time
** Added method for status segment size over time
* Captured login events
* Captured newsletter subscription/unsubscription
* Captured email address change events
* Captured paid subscription events
* Captured payment events
* Captured status events
