Add possibility to create virtual address book

[Mannshoch]

If possible I would like to share address books based on Categories.

I wish to share some personal data with other people by selected category and elements.
See Mokup

[jancborchardt]

This is out of scope for this app. There’s either:

• Sharing an address book, which is already possible
• Sharing a group: Ability to share groups #212
• Sharing individual contacts: Sharing single contacts and events #111

[Mannshoch]

thanks @jancborchardt for comment it. Yes this solution is maybe a bit much enhanced, thats why I created the simpler idea #212 .

[jancborchardt]

@Mannshoch yeah, thank you for all the testing and suggestions. :) Much appreciated.