title: ServiceNow Rest API OAuth returns not Authorized error
body: <p>I managed to access the Rest Api with Basic authentication with username and password.
  Now I am trying to access the Rest Api with OAuth.
  I was referring to <a href="http://http//wiki.servicenow.com/index.php?title=Generating_OAuth_Tokens#API_Request_Parameters&amp;gsc.tab=0" rel="nofollow">this article</a></p>
  
  <p>This is the format of the POST message I created (using Postman with Chrome),</p>
  
  <pre><code>POST /oauth_token.do HTTP/1.1
  Host: devxxxxx.service-now.com
  Accept: application/json
  Content-Type: application/json
  Authorization: Basic YWRtaW46Q0BycjBsMTIz
  Cache-Control: no-cache
  Content-Type: application/x-www-form-urlencoded
  </code></pre>
  
  <p>Url Encoded body:</p>
  
  <pre><code>grant_type=password&amp;client_id=xxxxxx&amp;client_secret=xxxxxx&amp;username=admin&amp;username=xxxxxx
  </code></pre>
  
  <p>I tried both encoded body and body without encoding, it gives the same result.</p>
  
  <p>Response</p>
  
  <pre><code>{
      "error": "server_error",
      "error_description": "access_denied"
  }
  </code></pre>
  
  <p>Am I missing something here? Doesn't the "admin" user has privileges to perform this operation and acquire tokens?</p>