title: DynamoDB ConditionalCheckFailedException - obtaining the item content that failed the test
body: <p>I'm using precondition expressions on <code>PutItem</code> and <code>UpdateItem</code> requests.</p>
  <p>Is there a way to achieve either or both of the following:</p>
  <ol>
  <li><p>not throw an exception - this is not an exceptional situation, it's an anticipated condition; as with validation of external inputs, I would like to be able to inspect the result without there being a throw and a catch - is there a way to achieve that?</p>
  </li>
  <li><p>given the server has just read the data in order to determine the check failed, is it possible to have it return it, given the RCUs have already been paid and the general pattern is that the before/after can be included as part of the roundtrip? Or is this a truly hard-baked service-side limitation? Would love to see a link to something authoritative as any docs I've traversed are silent on the matter...</p>
  </li>
  </ol>
  <p>(I'm using a current version of the .NET SDK <code>AWSSDK.DynamoDBv2</code> NuGet package.)</p>