Delete document with MongoSinkConnector

Question

I'm able to insert/update documents in mongo but i'm struggling to delete documents.

This is how the data is recorded in kafka topic by a debezium connect from a SQL Server source(the last row is how DELETE operation looks like):

{"user_code":1001}      {"user_code":1001,"first_name":"Sally","last_name":"Thomas","email":"[email protected]"}
{"user_code":1002}      {"user_code":1002,"first_name":"George","last_name":"Bailey","email":"[email protected]"}  
{"user_code":1003}      {"user_code":1003,"first_name":"Edward","last_name":"Walker","email":"[email protected]"}       
{"user_code":1003}      null

In this example even if after the NULL value, the document with user_code 1003 still in MongoDB.

Below is how I'm configuring my MongoSinkConnector (I've already tried both mongodb.delete.on.null.values and delete.on.null.values but none of them worked):

{
  "name": "inventory-connector-sink-2",
  "config": {
      "connector.class" : "com.mongodb.kafka.connect.MongoSinkConnector",
      "tasks.max" : "1",
      "topics": "server1.dbo.customers",
      "connection.uri": "mongodb://root:root@mongo:27017/",
      "database": "testDB",
      "collection": "customers_2",
      "database.history.kafka.bootstrap.servers" : "kafka:9092",
      "database.history.kafka.topic": "schema-changes.inventory",
      "key.converter": "org.apache.kafka.connect.json.JsonConverter",
      "key.converter.schemas.enable": false,
      "value.converter": "org.apache.kafka.connect.json.JsonConverter",
      "value.converter.schemas.enable": false,
      "document.id.strategy": "com.mongodb.kafka.connect.sink.processor.id.strategy.FullKeyStrategy",
      "writemodel.strategy":"com.mongodb.kafka.connect.sink.writemodel.strategy.ReplaceOneBusinessKeyStrategy",
      "mongodb.delete.on.null.values": true
  }
}

I've also tried using PartialValueStrategy but no luck.

PS: I'm working with confluentinc/cp-kafka-connect docker image for my sink connector.