Add option to disable account deletion for all accounts

Related problem to this feature:

I have added every account via occ mail:account:create and want to automate account management via scripts, so every mail account gets its own token. I have disabled the option to create new mailboxes, but every user can still delete the mailbox created via occ (and manage mail server settings). If I fake the account to be provisioned then this option (as well as mail server settings) is disabled, but the user can not create new alias adresses.

Feature:

So it would be nice to have an option for the server admin to disable account deletion, similar to the option which disables the creation of new mailboxes.

Possible workaround

Sadly, I was not able to disable the remove account button with css. This would be also a nice workaround if the button (as well with mail server settings) has a dedicated css class.

Start by locating the existing option that disables mailbox creation and trace its handling from the occ mail:account:create workflow through the account-management UI. Check how the remove-account button and mail-server settings are rendered; done means an administrator can disable deletion for all accounts without preventing alias creation, with the behavior covered by the relevant tests.