How to send Multipart form data from ServiceNow

I have to send attachments from ServiceNow to Jira using REST message. I cannot use plugins or Integration Hub. 

I have created a REST message for that -- 

Endpoint is -- https://******************/rest/api/3/issue/SSP-8441/attachments

In header I am sending--

Content-Diposition - form-data

Content-Type - multipart/form-data; boundary=AAA

X-Atlassian-Token - no-check

In the content I am sending the payload as

{
      "attachments": [{
          "content_type": "image/png",
          "file_name": "Screenshot (153).png",
                "size_bytes ": "137246 ",
          "sys_id": "f576b5211b091950f7b82fcde54bcbae",
"Content-Transfer-Encoding": "base64${base64EncodedData}"
      }]
  }

While testing 200 response code is coming, but no attachments being added to the Jira end