REST API exposes stack traces on error

[rspurgeon]

When POSTing invalid requests to the ksqlDB REST API server stack traces are presented to me in the response body.

Steps to reproduce the behavior, include:

1. ksqlDB version hosted in Confluent Cloud as of 5/18/2020
2. using curl, post an invalid request body, for example (notice a missing } bracket in the JSON body)
   "{"ksql": "CREATE STREAM pageviews WITH (kafka_topic='pageviews', value_format='AVRO');","streamsProperties": "ksql.streams.auto.offset.reset":"earliest","ksql.streams.cache.max.bytes.buffering":"0"}"

I'd expect to receive an error message, but not internal server stack traces.

Actual behaviour
I receive a stack trace similar to the following:

{"message": "Cannot construct instance of `java.util.LinkedHashMap` (although at least one Creator exists): no String-argument constructor/factory method to deserialize from String value ('ksql.streams.auto.offset.reset')\n at [Source: (org.glassfish.jersey.message.internal.ReaderInterceptorExecutor$UnCloseableInputStream); line: 1, column: 110] (through reference chain: io.confluent.ksql.rest.entity.KsqlRequest[\"streamsProperties\"])",
  "stackTrace": [
    "com.fasterxml.jackson.databind.exc.MismatchedInputException.from(MismatchedInputException.java:63)",
    "com.fasterxml.jackson.databind.DeserializationContext.reportInputMismatch(DeserializationContext.java:1429)",
    "com.fasterxml.jackson.databind.DeserializationContext.handleMissingInstantiator(DeserializationContext.java:1059)",
    "com.fasterxml.jackson.databind.deser.ValueInstantiator._createFromStringFallbacks(ValueInstantiator.java:371)",
    "com.fasterxml.jackson.databind.deser.ValueInstantiator.createFromString(ValueInstantiator.java:258)",
    "com.fasterxml.jackson.databind.deser.std.MapDeserializer.deserialize(MapDeserializer.java:357)",
...
...
...
    "org.eclipse.jetty.util.thread.QueuedThreadPool.runJob(QueuedThreadPool.java:806)",
    "org.eclipse.jetty.util.thread.QueuedThreadPool$Runner.run(QueuedThreadPool.java:938)",
    "java.base/java.lang.Thread.run(Thread.java:834)"
}