title: How to disable 'spark.security.credentials.${service}.enabled' in Structured streaming while connecting to a kafka cluster
body: <p>I am trying to read data from a secured Kafka cluster using spark structured streaming.
  Also I am using the below library to read the data - "spark-sql-kafka-0-10_2.12":"3.0.0-preview" since it has the feature to specify our custom group id (instead of spark setting its own custom group id)</p>
  
  <p>Dependency used in code:</p>
  
  <pre><code>        &lt;groupId&gt;org.apache.spark&lt;/groupId&gt;
          &lt;artifactId&gt;spark-sql-kafka-0-10_2.12&lt;/artifactId&gt;
          &lt;version&gt;3.0.0-preview&lt;/version&gt;
  </code></pre>
  
  <p>I am getting the below error - even after specifying the required JAAS configuration in spark options.</p>
  
  <p><strong>Caused by: java.lang.IllegalArgumentException: requirement failed: Delegation token must exist for this connector.</strong>
      at scala.Predef$.require(Predef.scala:281)
      at org.apache.spark.kafka010.KafkaTokenUtil$.isConnectorUsingCurrentToken(KafkaTokenUtil.scala:299)
      at org.apache.spark.sql.kafka010.KafkaDataConsumer.getOrRetrieveConsumer(KafkaDataConsumer.scala:533)
      at org.apache.spark.sql.kafka010.KafkaDataConsumer.$anonfun$get$1(KafkaDataConsumer.scala:275)</p>
  
  <p>Following document specifies that we can disable the feature of obtaining delegation token - <a href="https://spark.apache.org/docs/3.0.0-preview/structured-streaming-kafka-integration.html" rel="nofollow noreferrer">https://spark.apache.org/docs/3.0.0-preview/structured-streaming-kafka-integration.html</a></p>
  
  <p>I tried setting this property <code>spark.security.credentials.kafka.enabled</code> to <code>false</code> in spark config, but it is still failing with the same error.</p>