Introduce PaymentMetadata, PaymentMetadataStore, and PaymentDataWithFallback

- Add PaymentMetadata to represent metadata for inbound payments
- Add PaymentMetadataStore for persisting PaymentMetadata
- Add PaymentDataWithFallback to handle backward compatibility during the transition from legacy bolt11/bolt12 pending payments to the new PaymentMetadata format

Issue #425

Author: moisesPompilio

src/io/mod.rs

@@ -26,6 +26,8 @@ pub(crate) const PEER_INFO_PERSISTENCE_KEY: &str = "peers";
 /// The payment information will be persisted under this prefix.
 pub(crate) const PAYMENT_INFO_PERSISTENCE_PRIMARY_NAMESPACE: &str = "payments";
 pub(crate) const PAYMENT_INFO_PERSISTENCE_SECONDARY_NAMESPACE: &str = "";
+/// The metadata information will be persisted under this prefix.
+pub(crate) const PAYMENT_METADATA_INFO_PERSISTENCE_SECONDARY_NAMESPACE: &str = "metadata";
 
 /// The spendable output information used to persisted under this prefix until LDK Node v0.3.0.
 pub(crate) const DEPRECATED_SPENDABLE_OUTPUT_INFO_PERSISTENCE_PRIMARY_NAMESPACE: &str =

src/payment/mod.rs

@@ -19,7 +19,8 @@ pub use bolt12::Bolt12Payment;
 pub use onchain::OnchainPayment;
 pub use spontaneous::SpontaneousPayment;
 pub use store::{
-	ConfirmationStatus, LSPFeeLimits, PaymentDetails, PaymentDirection, PaymentKind, PaymentStatus,
+	ConfirmationStatus, JitChannelFeeLimits, LSPFeeLimits, PaymentDetails, PaymentDirection,
+	PaymentKind, PaymentMetadata, PaymentMetadataDetail, PaymentStatus,
 };
 pub use unified_qr::{QrPaymentResult, UnifiedQrPayment};