Following the earlier upload-photo route in the photo.js in routes/ folder write another API end-point upload-photos, and the corresponding function in the photoController.js in the controllers/ folder in backend to upload multiple files to the azure blob.
It is a complete backend issue.
The request format needs to be decided by the contributor with respect to how the current implementation of single photo file is implemented.
Tell me your approach in the Discord first than start to work on the issue.