Kafka Elasticsearch Connector Timestamps

I can see this has been discussed a few times here for instance but I think the solutions are out of date due to breaking changes in Elasticsearch.

I'm trying to convert a long/epoch field in my Json in my Kafka topic to an Elasticsearch date type which is pushed through the connector.

When I try to add a dynamic mapping, my Kafka connect updates fail because Im trying to apply two mappings to a field, _doc and kafkaconnect. This was a breaking change around version 6 I believe where you can only have one mapping per index.

{
    "index_patterns": [ "depart_details" ],
  "mappings": {
    "dynamic_templates": [
      {
        "scheduled_to_date": {
          "match":   "scheduled",
          "mapping": {
            "type": "date"
          }
        }
      } 
    ]
}}

I've now focussed on trying to translate the message at source in the connector by changing the field to a timestamp, time or date.

    "transforms.TimestampConverter.type": "org.apache.kafka.connect.transforms.TimestampConverter$Value",
        "transforms.TimestampConverter.field" : "scheduled",
        "transforms.TimestampConverter.target.type": "Timestamp"

However, any messages I try to send through this transformer fail with

Caused by: org.apache.kafka.connect.errors.DataException: Java class class java.util.Date does not have corresponding schema type.
    at org.apache.kafka.connect.json.JsonConverter.convertToJson(JsonConverter.java:604)
    at org.apache.kafka.connect.json.JsonConverter.convertToJson(JsonConverter.java:668)
    at org.apache.kafka.connect.json.JsonConverter.convertToJsonWithoutEnvelope(JsonConverter.java:574)
    at org.apache.kafka.connect.json.JsonConverter.fromConnectData(JsonConverter.java:324)
    at io.confluent.connect.elasticsearch.DataConverter.getPayload(DataConverter.java:181)
    at io.confluent.connect.elasticsearch.DataConverter.convertRecord(DataConverter.java:163)
    at io.confluent.connect.elasticsearch.ElasticsearchWriter.tryWriteRecord(ElasticsearchWriter.java:285)
    at io.confluent.connect.elasticsearch.ElasticsearchWriter.write(ElasticsearchWriter.java:270)
    at io.confluent.connect.elasticsearch.ElasticsearchSinkTask.put(ElasticsearchSinkTask.java:169)

Seems like a really common thing to need to do, but I don't see how to get a date or time field into Elastic through this connector in version 7?

The Confluent documentation states that the ES connector is currently not supported with ES 7.

According to this issue, it might suffice to change type.name=kafkaconnect to type.name=_doc in your connector configuration.