[OJS API 3.3.0] POST request create new submission file : file stage error

Hello,

Describe the issue or problem
After I have created a submission with /submissions, I wanted to add a file to it with /submissions/:submissionId/files. Unfortunately, I get the following error message “You must provide a file stage” with error 403 :

{
    "error": "api.submissionFiles.400.noFileStageId",
    "errorMessage": "You must provide a file stage."
}

But if you look at my body, I have a fileStage provided so I don’t understand what I am doing wrong and what I should change ?

Steps I took leading up to the issue
For example:

  1. Create a submission with /submissions
  2. You can reuse the following body for the POST request /submissions/:submissionId/files and for the submissionId you can use the id provided in step 1.
  3. For encoding my file in base64, I used : base64 -i test.pdf -o test.txt in my terminal.

What application are you using?
API OJS 3.3.0-20-22
I use Postman as a swagger to do my request

Additional information

See here for documentation about the POST request

Body used :

{
  "assocId": 1,
  "assocType": 1,
  "caption": "An example PDF file.",
  "copyrightOwner": "John Doe",
  "creator": {
    "en_US": "John Doe"
  },
  "dateCreated": "2023-10-01T12:00:00Z",
  "description": {
    "en_US": "This file contains the main submission document."
  },
  "file": "{{File}}",
  "fileId": 1, 
  "fileStage": 1, 
  "genreId": 1,  
  "language": "en",
  "name": {
    "en_US": "example.pdf"
  },
  "publisher": {
    "en_US": "Example Publisher"
  },
  "source": {
    "en_US": "Source of the document"
  },
  "sourceSubmissionFileId": null,
  "subject": {
    "en_US": "Research and Development"
  },
  "submissionId": 13,
  "terms": "Creative Commons Attribution",
  "updatedAt": "2023-10-01T12:00:00Z",
  "uploaderUserId": 20, 
  "viewable": true
}

/!\ I have got to change the body by removing one key between Creator and DateCreated because apparently this word is not allowed on this forum (look at API doc if you need to test with it)

For information {{file}} corresponds to the file in base64 encoding which I have stored in my Postman environment.

Hello, I am surprised to see no answer for this question. Is there another thread for any API related question ?