Subfolders shouldn't be taken into account for special roles

How to reproduce

Add new email account that has a subfolder called "inbox" and or "drafts". E.g.

    - INBOX
    - Drafts
    - ...
    - MyProject
      - Inbox
      - Accounting
      - 2020
      - Drafts
    - Other Folder

Expected behavior

The top-level mailboxes "INBOX" and "Drafts" are getting a dedicated icon and are moved to the top. Other folders, especially the subfolders "MyProject/Inbox" and "MyProject/Drafts" are treated and displayed as normal folders where they are.

Actual behavior

Subfolders "MyProject/Inbox" and "MyProject/Drafts" are treated as special role mailboxes and show up as an additional inbox (or drafts folder resp.) with the special icon etc on the top level (see screenshot).

Warning: Careful when testing code changes. The special role is assigned when adding the account to Nextcloud and will not be refreshed when reloading.

Mail app

Mail app version: 1.8.0 - master (c63a38f99ca2d1e061c2a3bcbe05552098d93b01)

Mailserver or service: Host Europe, I think it's Dovecot IMAP

Server configuration

PHP version: 7.4

Nextcloud Version: 20.0.5 - master (a308c9be90ba174154727c4239cd968707d4c7e8)

Client configuration

Browser: Firefox 84

Start by tracing special-role assignment during account creation and how mailbox paths are classified for display. Reproduce the account setup with nested Inbox and Drafts folders, then verify that only top-level role mailboxes receive special icons and placement while subfolders remain ordinary folders.