f - update docs

Author: jkczyz

lightning/src/offers/refund.rs

@@ -191,12 +191,15 @@ macro_rules! refund_builder_methods { (
 	///
 	/// Also, sets the metadata when [`RefundBuilder::build`] is called such that it can be used by
 	/// [`Bolt12Invoice::verify`] to determine if the invoice was produced for the refund given an
-	/// [`ExpandedKey`].
+	/// [`ExpandedKey`]. However, if [`RefundBuilder::path`] is called, then the metadata must be
+	/// included in each [`BlindedPath`] instead. In this case, use
+	/// [`Bolt12Invoice::verify_using_payer_data`].
 	///
 	/// The `payment_id` is encrypted in the metadata and should be unique. This ensures that only
 	/// one invoice will be paid for the refund and that payments can be uniquely identified.
 	///
 	/// [`Bolt12Invoice::verify`]: crate::offers::invoice::Bolt12Invoice::verify
+	/// [`Bolt12Invoice::verify_using_payer_data`]: crate::offers::invoice::Bolt12Invoice::verify_using_payer_data
 	/// [`ExpandedKey`]: crate::ln::inbound_payment::ExpandedKey
 	pub fn deriving_payer_id(
 		node_id: PublicKey, expanded_key: &ExpandedKey, nonce: Nonce,