code: public function shouldPostFieldsBeSigned(Request $request) {
          $returnValue = false;
          
          if ($request->hasHeader('Content-Type')) {
              $contentType = $request->getHeader('Content-Type');
              //TODO - not safe
              if ($contentType !== 'application/x-www-form-urlencoded') {
                  $returnValue = true;
              }
          }
  
          // Don't sign POST fields if the request uses POST fields and no files
          if ($request->getFileCount() == 0) {
              $returnValue = false;
          }
  
          return $returnValue;
      }
docs: Decide whether the post fields should be added to the base string that Oauth signs.
  Non-conformant APIs may require that this method be
  overwritten e.g. the Flickr API incorrectly adds the post fields when the Content-Type
  is 'application/x-www-form-urlencoded'
  
  @param $request
  @return bool Whether the post fields should be signed or not