title: issue with Full-Text-Search Query Execution in Neptune with iam DB authorization enabled
body: <p>I am trying to integrate ES with neptune for Full-Text-Search Query Execution. With IAM DB authorization enabled in neptune, it is not able to execute query and giving below error</p>
  <p><strong>{&quot;detailedMessage&quot;:&quot;The request signature we calculated does not match the signature you provided. Check your AWS Secret Access Key and signing method. Consult the service documentation for details.&quot;,&quot;code&quot;:&quot;AccessDeniedException&quot;,&quot;requestId&quot;:&quot;b4bbe6b7-8361-5c9b-1584-ba7a6a64a03c&quot;}</strong></p>
  <p>However with IAM DB authorization disabled, same query execution is working fine.</p>
  <p>I am generating AWS SIG4 signature and utilising in the header as part of the query. With IAM enabled , i can able to connect(status check) to neptune DB with same sig4 signature.</p>