MultiUploadWorker class final

Upload multiple files in a single multipart/form-data HTTP request.

Reuses the existing HttpUploadWorker native implementation which already supports the files array format.

Example:

await NativeWorkManager.enqueue(
  taskId: 'batch-upload',
  trigger: const TaskTrigger.oneTime(),
  worker: NativeWorker.multiUpload(
    url: 'https://api.example.com/photos',
    files: [
      const UploadFile(filePath: '/cache/photo1.jpg', fieldName: 'photos'),
      const UploadFile(filePath: '/cache/photo2.jpg', fieldName: 'photos'),
      const UploadFile(filePath: '/cache/document.pdf', fieldName: 'docs',
                       mimeType: 'application/pdf'),
    ],
    headers: {'Authorization': 'Bearer token'},
    additionalFields: {'albumId': '42'},
  ),
  constraints: const Constraints(requiresNetwork: true),
);