Default document for Mongo API should have an _id property

When customers create a document in the Data Explorer, the default property should be _id instead of id. In Mongo API, id doesn't have any special meaning while _id does.


Start in the Data Explorer document-creation flow described in the issue and locate where the default document property is initialized. Verify the Mongo API behavior, then confirm that newly created documents use _id rather than id and that the UI still displays and saves them correctly.

Written by the indexing model from the issue text.