title: Unable to convert to timestamp using Kafka timestampconvert
body: <p>I am using Kafka source JDBC connector to pull DB events and I am running the kafka connect in standalone mode. When I run this file, I get the shown error. Please help me.</p>
  
  <p>Code:</p>
  
  <pre><code>name=sailpointdb01107
  connector.class=io.confluent.connect.jdbc.JdbcSourceConnector
  tasks.max=1
  connection.password = xxxxx
  connection.url = jdbc:oracle:thin:@xxxxx:1521/xxxxx
  connection.user =xxxxx 
  query= SELECT * FROM (SELECT NAME, TO_TIMESTAMP('19700101', 'YYYYMMDD')+ NUMTODSINTERVAL(COMPLETED/1000,'SECOND') AS TASKFAILEDON FROM task WHERE COMPLETION_STATUS='Error')
  mode= timestamp
  timestamp.column.name=TASKFAILEDON
  topic.prefix=testing
  validate.non.null=false
  transforms=TimestampConverter
  transforms.TimestampConverter.type=org.apache.kafka.connect.transforms.TimestampConverter$Value
  transforms.TimestampConverter.format=yyyy-MM-dd
  transforms.TimestampConverter.target.type=Timestamp
  transforms.TimestampConverter.target.field=TASKFAILEDON
  </code></pre>
  
  <p>Error:</p>
  
  <pre><code>Error[2019-10-01 15:17:45,058] ERROR WorkerSourceTask{id=sailpointdb01107-0} Task threw an uncaught and unrecoverable exception (org.apache.kafka.connect.runtime.WorkerTask)
  org.apache.kafka.connect.errors.ConnectException: Tolerance exceeded in error handler
  
  Caused by: org.apache.kafka.connect.errors.ConnectException: Schema Schema{STRUCT} does not correspond to a known timestamp type format
          at org.apache.kafka.connect.transforms.TimestampConverter.timestampTypeFromSchema(TimestampConverter.java:406)
          at org.apache.kafka.connect.transforms.TimestampConverter.applyWithSchema(TimestampConverter.java:334)
          at org.apache.kafka.connect.transforms.TimestampConverter.apply(TimestampConverter.java:275)
          at org.apache.kafka.connect.runtime.TransformationChain.lambda$apply$0(TransformationChain.java:50)
          at org.apache.kafka.connect.runtime.errors.RetryWithToleranceOperator.execAndRetry(RetryWithToleranceOperator.java:128)
          at org.apache.kafka.connect.runtime.errors.RetryWithToleranceOperator.execAndHandleError(RetryWithToleranceOperator.java:162)
          ... 11 more
  [2019-10-01 15:17:45,059] ERROR WorkerSourceTask{id=sailpointdb01107-0} Task is being killed and will not recover until manually restarted (org.apache.kafka.connect.runtime.WorkerTask)
  </code></pre>