Option to disable showing system email in avatars' contacts menu

Steps

1. Setup a NC instance
2. Create accounts for many external people with email so they can receive an invitation and notifications
3. Create a Talk conversation with all people
4. Click on the three dots on a person's avatar in the participant list

Expected result

In the case of external people, we should not see their email address.

Actual result

There's an option to see and click an email address

I suggest to add an option to remove the EmailProvider in config.php or other. A quick hack is to remove https://github.com/nextcloud/server/blob/stable20/lib/private/Contacts/ContactsMenu/ActionProviderStore.php#L88 in config.php

Version

Nextcloud 20

@rullzer @ChristophWurst FYI