Allow to add multiple phone numbers to the profile

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Feature request

With this feature implemented https://github.com/nextcloud/server/issues/19575 (thanks a lot @miaulalala 🚀 )

I think we should make the profile page more flexible. Especially in a enterprise environment people usually have multiple phone numbers (mobile, landline,...). At the moment the system address book can contain only one phone number. Ideally the system address book would be as flexible with regard to type and number of entries like a regular address book. But as a first staring point allowing multiple phone numbers in the user profile would be already a great enhancement.

Start by reading the referenced nextcloud/server#19575 issue and the current user-profile and system address-book implementation. Determine how phone numbers are represented, including their types and storage, then define completion as allowing multiple numbers to be added and displayed without breaking existing profiles.