CSFLE with data key per document


I would like to implement Client-Side Field Level Encryption where each document (e.g. user) would be encrypted with its data key. This feature was mentioned keynote in 2019 on Field Level Encryption in MongoDB 4.2 (MongoDB World 2019 Keynote, part 4) - YouTube.

Until now I have managed to set up “per collection encryption” with defining $jsonSchema validation but this is not granular enough for my use case:

 const _key = await encryption.createDataKey('local', {
    keyAltNames: ['demo-data-key']
 await mongoose.connection.createCollection('Users', {
   validator: {
     $jsonSchema: {
        bsonType: 'object',
        properties: {
          lastName: {
            encrypt: {
              bsonType: 'string',
              keyId: [_key],
              algorithm: 'AEAD_AES_256_CBC_HMAC_SHA_512-Deterministic' }

Also in official documentation, this scenario is not covered because key always needs to be specified upfront and it is defined on collection or field level but never on document https://docs.mongodb.com/manual/reference/security-client-side-automatic-json-schema/

Any help, please?

Were you able to figure this out? I need the same.