title: rename index in elasticsearch with kafka sink
body: <p>I am using the following sink. Issue is that it sets the elasticsearch index name same as the topic. I want to have a different elasticseach index name. How can I achieve that. I am using confluent 4</p>
  
  <pre><code>{
    "name": "es-sink-mysql-foobar-02",
    "config": {
      "_comment": "-- standard converter stuff -- this can actually go in the worker config globally --",
      "connector.class": "io.confluent.connect.elasticsearch.ElasticsearchSinkConnector",
      "value.converter": "io.confluent.connect.avro.AvroConverter",
      "key.converter": "io.confluent.connect.avro.AvroConverter",
      "key.converter.schema.registry.url": "http://localhost:8081",
      "value.converter.schema.registry.url": "http://localhost:8081",
  
  
      "_comment": "--- Elasticsearch-specific config ---",
      "_comment": "Elasticsearch server address",
      "connection.url": "http://localhost:9200",
  
      "_comment": "Elasticsearch mapping name. Gets created automatically if doesn't exist  ",
      "type.name": "type.name=kafka-connect",
      "index.name": "asimtest",
      "_comment": "Which topic to stream data from into Elasticsearch",
      "topics": "mysql-foobar",
  
      "_comment": "If the Kafka message doesn't have a key (as is the case with JDBC source)  you need to specify key.ignore=true. If you don't, you'll get an error from the Connect task: 'ConnectException: Key is used as document id and can not be null.",
      "key.ignore": "true"
    }
  }
  </code></pre>