Add tests for the new flows, ensure the existing ones work:

• export aggregation to json/csv
• export full collection to json/csv
• export query without projection to json/csv
• export query with projection to json/csv
• export query with select fields to json/csv
• abort export in progress
• ensure abort on disconnect
• export _id field (nested)

Maybe also at least one test that passes every possible query option (skip, limit, sort, filter, project, collection).