Cdk ldk node (#904)

* feat: add LDK Node Lightning backend with comprehensive integration

- Add new cdk-ldk-node crate implementing Lightning backend using LDK Node
- Extend MintPayment trait with start/stop methods for processor lifecycle management
- Add LDK Node configuration support to cdk-mintd with chain source and gossip options
- Enhance mint startup/shutdown to properly manage payment processor lifecycle

---------

Co-authored-by: Erik <78821053+swedishfrenchpress@users.noreply.github.com>

crates/cdk-payment-processor/src/proto/mod.rs

@@ -37,6 +37,10 @@ impl From<CdkPaymentIdentifier> for PaymentIdentifier {
                 r#type: PaymentIdentifierType::CustomId.into(),
                 value: Some(payment_identifier::Value::Id(id)),
             },
+            CdkPaymentIdentifier::PaymentId(hash) => Self {
+                r#type: PaymentIdentifierType::PaymentId.into(),
+                value: Some(payment_identifier::Value::Hash(hex::encode(hash))),
+            },
         }
     }
 }

crates/cdk-payment-processor/src/proto/payment_processor.proto

@@ -46,6 +46,7 @@ enum PaymentIdentifierType {
   LABEL = 2;
   BOLT12_PAYMENT_HASH = 3;
   CUSTOM_ID = 4;
+  PAYMENT_ID = 5;
 }
 
 message PaymentIdentifier {