Collection and view creation changestream events will now contain an additional field "operationDescription.type" with the type of the collection/view created.

The new `type` field is placed inside the existing `operationDescription` object, so that the top-level fields for events do not change.

The value for the `operationDescription.type` field is determined as follows:

• if the original oplog entry is a "create" (collection) entry, then `operationDescription.type` will contain `collection`.
• if the original oplog entry is a command that creates a timeseries collection with "viewOn" starting with `system.buckets.`), then `operationDescription.type` will contain `timeseries`.
• if the original oplog entry is a command that creates a non-timeseries view (with "viewOn" being set but not starting with `system.buckets.`), then `operationDescription.type` will contain `view`.

The new `operationDescription.type` field will only be returned if the changestream was opened with the `showExpandedEvents` flag.

Description of Linked Ticket

Currently `create` events offer no explicit indication of the type of the namespace that’s been created. Clients have to parse it heuristically:

1. If there’s a collection UUID: type=collection.
2. Otherwise, if viewOn is a system.buckets collection: type=timeseries.
3. Otherwise, type=view.

This means clients have to know about all collection types. So were there to be some new collection type, the logic above would process it as a view. Moreover, a client that doesn’t want to care about time-series collections nonetheless has to filter them out explicitly.

It would seem better all around to add a “type” field to the event.