[tchapi]

An address book inside Postel, shown when Davis is configured.

• Browse and filter the cards of all address books, or pick one
• Create, edit and delete contacts, with undo; pictures with a crop
• Download a contact, a book or everything as .vcf; import .vcf files
• Possible duplicates pointed out on a card, and merged
• From mail: a known sender opens their card, an unknown one can be added

How it works (see docs/architecture.md):

• Only standard CardDAV after the login; the app key is the one Davis-specific part
• One row per card in the SQLite copy, synced by ETag difference
• Changes go to Davis first with If-Match, and are refused rather than written over a change made elsewhere
• Lines of a vCard that Postel does not show are written back exactly as they were read

The migration empties the contacts copy; it fills again on first use.