plugins/carddav: filter contacts with EMAIL/FN set

Don't issue a CardDAV query with any filter, Google won't return any
result.

plugins/carddav/plugin.go

@@ -121,6 +121,9 @@ func newPlugin(srv *koushin.Server) (koushin.Plugin, error) {
 			DataRequest: carddav.AddressDataRequest{
 				Props: []string{vcard.FieldFormattedName, vcard.FieldEmail},
 			},
+			PropFilters: []carddav.PropFilter{{
+				Name: vcard.FieldEmail,
+			}},
 		}
 		addrs, err := c.QueryAddressBook(addressBook.Path, &query)
 		if err != nil {

plugins/carddav/routes.go

@@ -38,6 +38,9 @@ func registerRoutes(p *plugin) {
 					vcard.FieldUID,
 				},
 			},
+			PropFilters: []carddav.PropFilter{{
+				Name: vcard.FieldFormattedName,
+			}},
 		}
 
 		if queryText != "" {