[{"key":1,"risks":[{"_id":"1234-risk1","name":"risk1"},{"_id":"9999-risk2","name":"risk2"}],"controls":[{"identifier":"P8.1.3","links":[{"entity":{"valueKey":"1234-risk1"}},{"entity":{"valueKey":"456"}}]},{"identifier":"X8.1.3","links":[{"entity":{"valueKey":"1234-risk1"}},{"entity":{"valueKey":"456"}}]},{"identifier":"Y8.1.3","links":[{"entity":{"valueKey":"9999-risk2"}},{"entity":{"valueKey":"456"}}]},{"identifier":"A1.2.9","links":[{"entity":{"valueKey":"456"}}]}]}]

db.collection.aggregate([])