Cannot Create New Account – "Error: Unauthorized" During Self-Registration

[mababict]

When trying to create a new account using the public "Create your new account" form, the following error occurs immediately after submitting the form:

Error: Unauthorized

This happens even if all required fields (email address, password, confirm password, language) are correctly filled in.
The system does not proceed to validate the form data, but instead blocks the request with an Unauthorized error.

Steps to Reproduce:

Navigate to the registration page (/register or /signup).

Fill in all required fields (email, password, confirm password, language).

Click Create Account.

Observe the red error notification: "Error: Unauthorized".

Expected Behaviour:
New users should be able to create an account successfully, or at least receive a detailed error if registration is restricted.

Actual Behaviour:
The system immediately returns an Unauthorized error without creating the user or validating input.

Environment:

System: Synology NAS (Docker Deployment)

Application: Peppermint Helpdesk

Deployment: Docker container (managed via Synology DSM)

Version: [please specify version if known]

Additional Information:

No modifications were made to the registration form.

It is unclear whether public registration is currently enabled or supported by default.

Docker networking uses the Synology default bridge mode.