closes: https://github.com/TryGhost/Ghost/issues/14640
- eu mailgun domains have a different structure.
- we weren't accounting for this when fetching the next page of results, meaning that email stats didn't work on EU domains
refs https://github.com/TryGhost/Ghost/pull/12541
- make `EventProcessor` a super-class designed to be inherited from in consumer applications for application-level implementation
- helps to keep application-level concerns for event handling (eg, what to do with spam complaints) and things like application database knowledge in the consumer
- removed all database knowledge from `EmailAnalyticsService`
- requires a `queries` option to be passed in that lets the consuming application provide knowledge and define how fetched stats should be 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
