Group pending payment storage constants

Keep pending payment namespace constants next to the primary payment
store constants.

This keeps related persistence keys discoverable together.

Co-Authored-By: HAL 9000

Author: tnull

src/io/mod.rs

@@ -29,6 +29,10 @@ pub(crate) const PEER_INFO_PERSISTENCE_KEY: &str = "peers";
 pub(crate) const PAYMENT_INFO_PERSISTENCE_PRIMARY_NAMESPACE: &str = "payments";
 pub(crate) const PAYMENT_INFO_PERSISTENCE_SECONDARY_NAMESPACE: &str = "";
 
+/// The pending payment information will be persisted under this prefix.
+pub(crate) const PENDING_PAYMENT_INFO_PERSISTENCE_PRIMARY_NAMESPACE: &str = "pending_payments";
+pub(crate) const PENDING_PAYMENT_INFO_PERSISTENCE_SECONDARY_NAMESPACE: &str = "";
+
 /// The node metrics will be persisted under this key.
 pub(crate) const NODE_METRICS_PRIMARY_NAMESPACE: &str = "";
 pub(crate) const NODE_METRICS_SECONDARY_NAMESPACE: &str = "";
@@ -80,7 +84,3 @@ pub(crate) const BDK_WALLET_INDEXER_KEY: &str = "indexer";
 ///
 /// [`StaticInvoice`]: lightning::offers::static_invoice::StaticInvoice
 pub(crate) const STATIC_INVOICE_STORE_PRIMARY_NAMESPACE: &str = "static_invoices";
-
-/// The pending payment information will be persisted under this prefix.
-pub(crate) const PENDING_PAYMENT_INFO_PERSISTENCE_PRIMARY_NAMESPACE: &str = "pending_payments";
-pub(crate) const PENDING_PAYMENT_INFO_PERSISTENCE_SECONDARY_NAMESPACE: &str = "";