Add admin UI for IONOS mailbox management

[Copilot]

Implements mailbox administration interface in admin settings for managing IONOS email accounts. Admins can list all mailboxes, edit email localparts, and delete accounts.

Backend

API Controller (MailboxAdminController)

• GET /api/admin/mailboxes - Lists all IONOS mailboxes with linked user info
• PATCH /api/admin/mailboxes/{userId} - Updates email localpart with duplicate detection
• DELETE /api/admin/mailboxes/{userId} - Deletes mailbox via IONOS provider

Service Layer (MailboxAdminService)

• Iterates all Nextcloud users to find IONOS mailboxes
• Validates localpart format: /^[a-zA-Z0-9._-]+$/
• Case-insensitive duplicate email detection
• Delegates to existing IonosProviderFacade (no provider changes required)

Access restricted via @AuthorizedAdminSetting annotation.

Frontend

MailboxManagement.vue

• Table view with columns: email address, user (avatar + display name + username)
• Inline edit modal for localpart changes
• Delete confirmation modal with data loss warning
• Error handling for validation failures and network issues

MailboxListItem.vue

• Row component with action menu (edit/delete)
• Uses Nextcloud's NcAvatar, NcActions, NcModal components

Integrated into AdminSettings.vue as "E-Mail Verwaltung" section.

Example Usage

Edit flow validation:

// Valid localpart change
PATCH /api/admin/mailboxes/user123
{ "newLocalpart": "john.doe" }
→ 200 { "success": true, "email": "john.doe@domain.com" }

// Duplicate detection
PATCH /api/admin/mailboxes/user456
{ "newLocalpart": "john.doe" }
→ 400 { "success": false, "error": "Email is already taken. Please use some other username." }

Admin documentation added to doc/admin.md.

Warning

Firewall rules blocked me from connecting to one or more addresses (expand for details)

I tried to connect to the following addresses, but was blocked by firewall rules:

• https://api.github.com/repos/ArthurHoaro/favicon/zipball/2f2af255e4a2ea0abff2a1b34b51cf4e57e6a230
  • Triggering command: /usr/bin/php8.3 /usr/bin/php8.3 -n -c /tmp/WmiSGC /usr/bin/composer install (http block)
• https://api.github.com/repos/amphp/amp/zipball/ded3d9be08f526089eb7ee8d9f16a9768f9dec2d
  • Triggering command: /usr/bin/php8.3 /usr/bin/php8.3 -n -c /tmp/WmiSGC /usr/bin/composer install (http block)
• https://api.github.com/repos/amphp/byte-stream/zipball/4f0e968ba3798a423730f567b1b50d3441c16ddc
  • Triggering command: /usr/bin/php8.3 /usr/bin/php8.3 -n -c /tmp/WmiSGC /usr/bin/composer install (http block)
• https://api.github.com/repos/amphp/parser/zipball/3cf1f8b32a0171d4b1bed93d25617637a77cded7
  • Triggering command: /usr/bin/php8.3 /usr/bin/php8.3 -n -c /tmp/WmiSGC /usr/bin/composer install (http block)
• https://api.github.com/repos/amphp/process/zipball/55b837d4f1857b9bd7efb7bb859ae6b0e804f13f
  • Triggering command: /usr/bin/php8.3 /usr/bin/php8.3 -n -c /tmp/WmiSGC /usr/bin/composer install (http block)
• https://api.github.com/repos/amphp/serialization/zipball/693e77b2fb0b266c3c7d622317f881de44ae94a1
  • Triggering command: /usr/bin/php8.3 /usr/bin/php8.3 -n -c /tmp/WmiSGC /usr/bin/composer install (http block)
• https://api.github.com/repos/amphp/sync/zipball/85ab06764f4f36d63b1356b466df6111cf4b89cf
  • Triggering command: /usr/bin/php8.3 /usr/bin/php8.3 -n -c /tmp/WmiSGC /usr/bin/composer install (http block)
• https://api.github.com/repos/bamarni/composer-bin-plugin/zipball/92fd7b1e6e9cdae19b0d57369d8ad31a37b6a880
  • Triggering command: /usr/bin/php8.3 /usr/bin/php8.3 -n -c /tmp/WmiSGC /usr/bin/composer install (http block)

If you need me to access, download, or install something from one of these locations, you can either:

• Configure Actions setup steps to set up my environment, which run before the firewall is enabled
• Add the appropriate URLs or hosts to the custom allowlist in this repository's Copilot coding agent settings (admins only)

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