internal: add PROPPATCH support to server

carddav/server.go

@@ -261,6 +261,10 @@ func (b *backend) propfindAddressObject(propfind *internal.Propfind, ao *Address
 	return internal.NewPropfindResponse(ao.Href, propfind, props)
 }
 
+func (b *backend) Proppatch(r *http.Request, update *internal.Propertyupdate) (*internal.Response, error) {
+	panic("TODO")
+}
+
 func (b *backend) Put(r *http.Request) error {
 	panic("TODO")
 }