[files_external] do not offer local storage for users

[susnux]

You cannot create a user external storages as local backend.
This is only possible for admin external storages.

➡️ in the user settings it must not be shown...

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Screenshot of the settings in question

Screenshot showing error

Request was to /apps/files_external/userstorages
Request Headers

POST /apps/files_external/userstorages HTTP/1.1
Accept: application/json, text/plain, */*
Accept-Encoding: gzip, deflate, br, zstd
Accept-Language: en-US,en;q=0.9
Authorization: Basic xxx
Cache-Control: no-cache
Connection: keep-alive
Content-Length: 283
Content-Type: application/json
Cookie: oc_sessionPassphrase=xxx
Host: xxx
Origin: xxx
Pragma: no-cache
Sec-Fetch-Dest: empty
Sec-Fetch-Mode: cors
Sec-Fetch-Site: same-origin
User-Agent: Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/144.0.0.0 Safari/537.36
X-Requested-With: XMLHttpRequest, XMLHttpRequest
requesttoken: xxx
sec-ch-ua: "Not(A:Brand";v="8", "Chromium";v="144", "Google Chrome";v="144"
sec-ch-ua-mobile: ?0
sec-ch-ua-platform: "Linux"

Response Headers

HTTP/1.1 403 Forbidden
Server: nginx/1.26.2
Date: Mon, 09 Mar 2026 15:36:27 GMT
Content-Type: application/json; charset=utf-8
Content-Length: 46
Connection: keep-alive
Cache-Control: no-cache, no-store, must-revalidate
Content-Security-Policy: default-src 'none';base-uri 'none';manifest-src 'self';frame-ancestors 'none'
Feature-Policy: autoplay 'none';camera 'none';fullscreen 'none';geolocation 'none';microphone 'none';payment 'none'
Referrer-Policy: no-referrer
Set-Cookie: xxx; path=/; secure; HttpOnly; SameSite=Lax
Strict-Transport-Security: max-age=31536000;
Via: 1.1 Caddy
X-Content-Type-Options: nosniff
X-Frame-Options: SAMEORIGIN
X-Permitted-Cross-Domain-Policies: none
X-Request-Id: IFcy1bt9H0GE6nC3JKFc
X-Robots-Tag: noindex, nofollow
X-User-Id: admin

Response

{"message":"Forbidden to manage local mounts"}

System Settings

This request was made with the admin user. It is not forbidden from doing anything (tell me how to provide proof of this)

There is nothing in the docker compose logs so I don't know how to get you anything more than this. I can appreciate that you are not able to recreate this ondemand. I can, so please tell me what you need and I am more than happy to provide it.

Originally posted by @miversen33 in #53472

[susnux]

#57917