code: private function buildRequestHeaders($name, $request, $body)
      {
          $headers = [];
  
          if ($request->hasAttachment()) {
              $headers['Content-Type'] = 'multipart/related;boundary=MIME_boundary;type="application/xop+xml";start="<request.xml@devbay.net>";start-info="text/xml"';
          } else {
              $headers['Content-Type'] = 'text/xml';
          }
  
          if ($this->getConfig('compressResponse')) {
              $headers[self::HDR_RESPONSE_ENCODING] = 'application/gzip';
          }
  
          $headers['Content-Length'] = strlen($body);
  
          return array_merge($headers, $this->getEbayHeaders($name));
      }
docs: Helper function that builds the HTTP request headers.
  
  @param string $name The name of the operation.
  @param \DTS\eBaySDK\Types\BaseType $request Request object containing the request information.
  @param string $body The request body.
  
  @return array An associative array of HTTP headers.