Store LSPFeeLimits in metadata store for JIT channel payments

In `receive_via_jit_channel_inner`, insert a
`PaymentMetadataKind::LSPFeeLimits` entry into the
`PaymentMetadataStore` so JIT channel fee limits are persisted
independently of the `PaymentStore` entry.

In the `PaymentClaimable` event handler, add a fallback path that
checks the metadata store for LSP fee limits when the `PaymentKind`
doesn't carry them directly.

Generated with the assistance of AI tools.

Co-Authored-By: HAL 9000

Author: tnull

src/event.rs

@@ -750,7 +750,21 @@ where
 								})
 								.unwrap_or(0)
 						},
-						_ => 0,
+						_ => {
+							// Fallback: check the metadata store for LSP fee limits.
+							self.payment_metadata_store
+								.get_lsp_fee_limits_for_payment_id(&payment_id)
+								.and_then(|limits| {
+									limits.max_total_opening_fee_msat.or_else(|| {
+										limits.max_proportional_opening_fee_ppm_msat.and_then(
+											|max_prop_fee| {
+												compute_opening_fee(amount_msat, 0, max_prop_fee)
+											},
+										)
+									})
+								})
+								.unwrap_or(0)
+						},
 					};
 
 					if counterparty_skimmed_fee_msat > max_total_opening_fee_msat {

src/payment/bolt11.rs

@@ -18,6 +18,7 @@ use lightning::ln::channelmanager::{
 };
 use lightning::ln::outbound_payment::{Bolt11PaymentError, Retry, RetryableSendFailure};
 use lightning::routing::router::{PaymentParameters, RouteParameters, RouteParametersConfig};
+use lightning::sign::EntropySource;
 use lightning_invoice::{
 	Bolt11Invoice as LdkBolt11Invoice, Bolt11InvoiceDescription as LdkBolt11InvoiceDescription,
 };
@@ -30,7 +31,9 @@ use crate::error::Error;
 use crate::ffi::{maybe_deref, maybe_try_convert_enum, maybe_wrap};
 use crate::liquidity::LiquiditySource;
 use crate::logger::{log_error, log_info, LdkLogger, Logger};
-use crate::payment::metadata_store::PaymentMetadataStore;
+use crate::payment::metadata_store::{
+	MetadataId, PaymentMetadataEntry, PaymentMetadataKind, PaymentMetadataStore,
+};
 use crate::payment::store::{
 	LSPFeeLimits, PaymentDetails, PaymentDetailsUpdate, PaymentDirection, PaymentKind,
 	PaymentStatus,
@@ -212,6 +215,16 @@ impl Bolt11Payment {
 			max_proportional_opening_fee_ppm_msat: lsp_prop_opening_fee,
 		};
 		let id = PaymentId(payment_hash.0);
+
+		// Store LSP fee limits in the metadata store.
+		let metadata_id = MetadataId { id: self.keys_manager.get_secure_random_bytes() };
+		let metadata_entry = PaymentMetadataEntry {
+			id: metadata_id,
+			kind: PaymentMetadataKind::LSPFeeLimits { limits: lsp_fee_limits },
+			payment_ids: vec![id],
+		};
+		self.payment_metadata_store.insert(metadata_entry)?;
+
 		let preimage =
 			self.channel_manager.get_payment_preimage(payment_hash, payment_secret.clone()).ok();
 		let kind = PaymentKind::Bolt11Jit {