Is your feature request related to a problem? Please describe.

As a Nextcloud user I want to be able to import .vcf files from Nextcloud files to one of my address books on any platform. Right now this only works for web.

Describe the solution you'd like

Declare an action for vcf mime files that shows a simple address book selector to the user. The client sends a request with file id and address book ID to a new endpoint, which fetches the file, splits the vcards and pushes them to the specified address book.

Describe alternatives you've considered

N/a

Work packages

• Extend OCP API to create contacts from string.
• Implement OCS API in Contacts to import contacts from a file by id.

Follow-ups

• Use the new endpoint for the web import too to deduplicate code

Additional context

• Declarative protocol: dynamic menu entries in clients files-clients#86 (comment)
• Sibling of Declarative ui: a quick way to create a new contact in Contacts #4630