refs https://github.com/TryGhost/Team/issues/1277
- In `getEventTimeline` we filter to only perform the relevant queries, passing to each query function the filters (subset of NQL)
- In each query function, we rewrite the filters to adapt them to the internal data shape.
- We need to do this rewrite to allow API consumers to create filters based on the output on the API instead of the internal data structure.
- Added partial unit tests as there is a lot of repetition between the query functions.
refs https://github.com/TryGhost/Team/issues/1277
- This will allow to filter events within `getEventTimeline`
- The subset of NQL has the following rules:
- Only one level of filters, now parenthesis allowed
- Only three filter keys allowed
- No `or` allowed outside of the bracket notation (this is allowed: `type:-[email_opened_event,email_failed_event]` but this isn't: `type:1,data.created_at:1`)
- The return is an object with a NQL filter by allowed filter key
