Attributable failures optional feature bit

Signal to senders that the node will return attributable failures. When
the sender makes sure all path nodes supports this, they will be able to
attribute every failure that may occur.

Author: joostjager

lightning-types/src/features.rs

@@ -154,7 +154,7 @@ mod sealed {
 			// Byte 3
 			RouteBlinding | ShutdownAnySegwit | DualFund | Taproot,
 			// Byte 4
-			Quiescence | OnionMessages,
+			Quiescence | OnionMessages | AttributableFailures,
 			// Byte 5
 			ProvideStorage | ChannelType | SCIDPrivacy,
 			// Byte 6
@@ -175,7 +175,7 @@ mod sealed {
 			// Byte 3
 			RouteBlinding | ShutdownAnySegwit | DualFund | Taproot,
 			// Byte 4
-			Quiescence | OnionMessages,
+			Quiescence | OnionMessages | AttributableFailures,
 			// Byte 5
 			ProvideStorage | ChannelType | SCIDPrivacy,
 			// Byte 6
@@ -199,7 +199,7 @@ mod sealed {
 		// Byte 3
 		,
 		// Byte 4
-		,
+		AttributableFailures,
 		// Byte 5
 		,
 		// Byte 6
@@ -219,7 +219,7 @@ mod sealed {
 		// Byte 3
 		,
 		// Byte 4
-		,
+		AttributableFailures,
 		// Byte 5
 		,
 		// Byte 6
@@ -548,6 +548,16 @@ mod sealed {
 		supports_quiescence,
 		requires_quiescence
 	);
+	define_feature!(
+		37,
+		AttributableFailures,
+		[InitContext, NodeContext, Bolt11InvoiceContext, Bolt12InvoiceContext],
+		"Feature flags for `option_attributable_failures`.",
+		set_attributable_failures_optional,
+		set_attributable_failures_required,
+		supports_attributable_failures,
+		requires_attributable_failures
+	);
 	define_feature!(
 		39,
 		OnionMessages,