refs https://github.com/TryGhost/Ghost/issues/12421
requires https://github.com/TryGhost/Ghost/pull/12457
- updates stats aggregator to calculate and store an open rate for each member
- uses two queries because I couldn't find a reasonable approach to perform the update in a single query as per the email aggregation
- benchmarked locally at <1sec/1000members
- will not store an open rate unless the number of tracked emails sent to a member is above a certain threshold (defaults to 5) to avoid new members being heavily weighted
- fixes typo in EmailAnalytics that was stopping member stats from being aggregated
no issue
- added `EmailAnalyticsService`
- `.fetchAll()` grabs and processes all available events
- `.fetchLatest()` grabs and processes all events since the last seen event timestamp
- `EventProcessor` passed event objects and updates `email_recipients` or `members` records depending on the event being analytics or list hygiene
- always returns a `EventProcessingResult` instance so that progress can be tracked and merged across individual events, batches (pages of events), and total runs
- adds email_id and member_id to the returned result where appropriate so that the stats aggregator can limit processing to data that has changed
- sets `email_recipients.{delivered_at, opened_at, failed_at}` for analytics events
- sets `members.subscribed = false` for permanent failure/unsubscribed/complained list hygiene events
- `StatsAggregator` takes an `EventProcessingResult`-like object containing arrays of email ids and member ids on which to aggregate statistics.
- jobs for `fetch-latest` and `fetch-all` ready for use with the JobsService
- added `initialiseRecurringJobs()` function to Ghost bootup procedure that schedules the email analytics "fetch latest" job to run every minute
