Link to LSP spec in accept_underpaying_htlcs config

Author: valentinewallace

lightning/src/util/config.rs

@@ -462,8 +462,9 @@ pub struct ChannelConfig {
 	/// - The counterparty will get an [`HTLCIntercepted`] event upon payment forward, and call
 	///   [`forward_intercepted_htlc`] with less than the amount provided in
 	///   [`HTLCIntercepted::expected_outbound_amount_msat`]. The difference between the expected and
-	///   actual forward amounts is their fee.
-	// TODO: link to LSP JIT channel invoice generation spec when it's merged
+	///   actual forward amounts is their fee. See
+	///   <https://github.com/BitcoinAndLightningLayerSpecs/lsp/tree/main/LSPS2#flow-lsp-trusts-client-model>
+	///   for how this feature may be used in the LSP use case.
 	///
 	/// # Note
 	/// It's important for payee wallet software to verify that [`PaymentClaimable::amount_msat`] is