我使用的kafkaconnect-mongosource配置如下：

curl -X PUT http://localhost:8083/connectors/mongo-source2/config -H "Content-Type: application/json" -d '{
  "name":"mongo-source2",
  "tasks.max":1,
  "connector.class":"com.mongodb.kafka.connect.MongoSourceConnector",
  "key.converter":"org.apache.kafka.connect.storage.StringConverter",
  "value.converter":"org.apache.kafka.connect.storage.StringConverter",
  "connection.uri":"mongodb://xxx:xxx@localhost:27017/mydb",
  "database":"mydb",
  "collection":"claimmappingrules.66667777-8888-9999-0000-666677770000",
  "pipeline":"[{\"$addFields\": {\"something\":\"xxxx\"} }]",
  "transforms":"dropTopicPrefix",
  "transforms.dropTopicPrefix.type":"org.apache.kafka.connect.transforms.RegexRouter",
  "transforms.dropTopicPrefix.regex":".*",
  "transforms.dropTopicPrefix.replacement":"my-topic"
}'

出于某种原因，当我使用消息时，我会得到一个奇怪的密钥：

"_id": {
"_data": "825DFD2A53000000012B022C0100296E5A1004060C0FB7484A4990A7363EF5F662CF8D465A5F6964005A1003F9974744D06AFB498EF8D78370B0CD440004"
  }

我不知道它是从哪里来的，我的mongo文档的id是uuid，当我消费消息时，我希望在我的消费者密钥处看到documentkey字段。
以下是连接器发布到Kafka的消息示例：

{
  "_id": {
    "_data": "825DFD2A53000000012B022C0100296E5A1004060C0FB7484A4990A7363EF5F662CF8D465A5F6964005A1003F9974744D06AFB498EF8D78370B0CD440004"
  },
  "operationType": "replace",
  "clusterTime": {
    "$timestamp": {
      "t": 1576872531,
      "i": 1
    }
  },
  "fullDocument": {
    "_id": {
      "$binary": "+ZdHRNBq+0mO+NeDcLDNRA==",
      "$type": "03"
    },
    ...
  },
  "ns": {
    "db": "security",
    "coll": "users"
  },
  "documentKey": {
    "_id": {
      "$binary": "+ZdHRNBq+0mO+NeDcLDNRA==",
      "$type": "03"
    }
  }
}