fix: use 'file' field name with proper MIME type for attach endpoint

backend/helpers/ivantiApi.js

@@ -109,11 +109,11 @@ function ivantiFormPost(urlPath, fields, files, apiKey, skipTls) {
     }
 
     // File fields
-    for (const { name, buffer, filename } of files) {
+    for (const { name, buffer, filename, contentType } of files) {
         parts.push(Buffer.from(
             `--${boundary}\r\n` +
             `Content-Disposition: form-data; name="${name}"; filename="${filename}"\r\n` +
-            `Content-Type: application/octet-stream\r\n\r\n`
+            `Content-Type: ${contentType || 'application/octet-stream'}\r\n\r\n`
         ));
         parts.push(buffer);
         parts.push(Buffer.from('\r\n'));