How do I convert this mailgun multi attachment cURL request to UrlFetchApp?

Thanks to @Kos and his first comment I got inspiration from MailGun API Python Requests so I can post working code how to send multiple attachments using GAS and mailgun.

function sendEmail(email) {        var params = {    "from": email.fromName+" <"+email.fromEmail+">",    "to": email.toEmail,    "subject": email.subject,    "replyto": email.fromEmail,        "text": email.message,    "html": email.htmlMessage,  }      if ("attachments" in email){      for(var i=0, len=email.attachments.length; i < len; i++){        const fileId =  email.attachments[i]        const file = DriveApp.getFileById(fileId);          var attachmentBlob = file.getBlob()        params["attachment["+i+"]"] = attachmentBlob      }  }  if ( "bcc" in email){    params.bcc = email.bcc  }  var options = {    'method': 'post',    'payload': params,    'headers': {      'Authorization': 'Basic ' + Utilities.base64Encode("api:" + MAILGUN_KEY)    }  }  var response = JSON.parse(UrlFetchApp.fetch(email.url, options))}

where the email data object could look like

  var email ={}  email.toEmail = "TOemail@email.cz"  email.fromEmail = "fromEmail@email.cz"  email.fromName = "From email name"  email.subject = "From email name"  email.message = textVersionOfEmail  email.htmlMessage = hTMLVersionOfEmail  email.attachments = []  email.attachments.push(file1ID)  email.attachments.push(file2ID)

If you know how to be able to name files in the script please leave a note.