Add script to change Super Admin

[bothored]

This adds a script to give a new user Super Admin privileges.

This is most likely going to occur if someone starts with built-in authentication and moves to SSO, and their new username doesn't match. Therefore the howto/SSO.md references the script. Happy to add to any other parts of the docs if it makes sense.

The script will:

• Take the new username and path to the users.json
• Validate the user exists and it can find the current super admin
• Demote the current super admin (leaving it as Admin still)
• Promote the new super admin (setting both isSuperAdmin and isAdmin in case it wasn't already admin)
• The original users.json is backed up to users.json.bak in case they want to revert

As it is a bash script and therefore has no unit tests, here are the tests:

# original users.json
[
  {
    "username": "joe",
    "passwordHash": "<snip>",
    "isAdmin": true,
    "isSuperAdmin": true,
    "failedLoginAttempts": 0,
    "lastLogin": "2026-02-15T09:30:31.816Z"
  },
  {
    "username": "fred",
    "passwordHash": "<snip>",
    "isAdmin": true,
    "createdAt": "2026-02-13T09:18:08.887Z",
    "lastLogin": "2026-02-13T09:18:17.629Z",
    "preferredDateFormat": "dd/mm/yyyy",
    "preferredTimeFormat": "12-hours",
    "handedness": "right-handed",
    "failedLoginAttempts": 0,
    "isSuperAdmin": false
  }
]

bash scripts/update-super-admin.sh fred data/users/users.json
Current super admin is: joe
Demoting...
Promoting new super admin: fred
Backing up existing users.json to: data/users/users.json.bak
Updating data/users/users.json.
Done. Remove data/users/users.json.bak after verifying result.

# New users.json
[
  {
    "username": "joe",
    "passwordHash": "<snip>",
    "isAdmin": true,
    "isSuperAdmin": false,
    "failedLoginAttempts": 0,
    "lastLogin": "2026-02-15T09:30:31.816Z"
  },
  {
    "username": "fred",
    "passwordHash": "<snip>",
    "isAdmin": true,
    "createdAt": "2026-02-13T09:18:08.887Z",
    "lastLogin": "2026-02-13T09:18:17.629Z",
    "preferredDateFormat": "dd/mm/yyyy",
    "preferredTimeFormat": "12-hours",
    "handedness": "right-handed",
    "failedLoginAttempts": 0,
    "isSuperAdmin": true
  }
]

# Malformed JSON text (removed a random `}`)
bash scripts/update-super-admin.sh fred data/users/users.json
jq: parse error: Unmatched ']' at line 22, column 1
The user fred does not exist.

# No current Super Admin
[
  {
    "username": "joe",
    "passwordHash": "<snip>",
    "isAdmin": true,
    "isSuperAdmin": false,
    "failedLoginAttempts": 0,
    "lastLogin": "2026-02-15T09:30:31.816Z"
  },
  {
    "username": "fred",
    "passwordHash": "<snip>",
    "isAdmin": true,
    "createdAt": "2026-02-13T09:18:08.887Z",
    "lastLogin": "2026-02-13T09:18:17.629Z",
    "preferredDateFormat": "dd/mm/yyyy",
    "preferredTimeFormat": "12-hours",
    "handedness": "right-handed",
    "failedLoginAttempts": 0,
    "isSuperAdmin": false
  }
]

bash scripts/update-super-admin.sh fred data/users/users.json
No existing super admin found. Aborting.

To be explicit on the topic as I'm a new contributor - all code written is written by me directly.

[fccview]

This is fantastic!
Gonna test it out as soon as I have a minute and get it merged, thank you for this great contribution!

[fccview]

merged, stellar work! ❤️

[bothored]

merged, stellar work! ❤️

Thanks!