[ CCode ( cname = "E_BOOK_BACKEND_PROPERTY_REQUIRED_FIELDS" ) ]
[ Version ( since = "3.2" ) ]
public const string BOOK_BACKEND_PROPERTY_REQUIRED_FIELDS
Provides comma-separated list of required fields by the book backend.
All of these attributes should be set, otherwise the backend will reject saving the contact.
The field_id can be used to transform the field name into an ContactField.