lnwallet: add new aux resolver interface

This will be used by external callers to modify the way we resolve
contracts on chain. For a given contract, we'll store an extra "blob",
that will later be presented during the sweeping phase.

lnwallet/aux_resolutions.go

@@ -0,0 +1,89 @@
+package lnwallet
+
+import (
+	"github.com/btcsuite/btcd/btcutil"
+	"github.com/btcsuite/btcd/wire"
+	"github.com/lightningnetwork/lnd/fn"
+	"github.com/lightningnetwork/lnd/input"
+	"github.com/lightningnetwork/lnd/lnwire"
+	"github.com/lightningnetwork/lnd/tlv"
+)
+
+// CloseType is an enum that represents the type of close that we are trying to
+// resolve.
+type CloseType uint8
+
+const (
+	// LocalForceClose represents a local force close.
+	LocalForceClose CloseType = iota
+
+	// RemoteForceClose represents a remote force close.
+	RemoteForceClose
+
+	// Breach represents a breach by the remote party.
+	Breach
+)
+
+// ResolutionReq is used to ask an outside sub-system for additional
+// information needed to resolve a contract.
+type ResolutionReq struct {
+	// ChanPoint is the channel point of the channel that we are trying to
+	// resolve.
+	ChanPoint wire.OutPoint
+
+	// ShortChanID is the short channel ID of the channel that we are
+	// trying to resolve.
+	ShortChanID lnwire.ShortChannelID
+
+	// Initiator is a bool if we're the initiator of the channel.
+	Initiator bool
+
+	// CommitBlob is an optional commit blob for the channel.
+	CommitBlob fn.Option[tlv.Blob]
+
+	// FundingBlob is an optional funding blob for the channel.
+	FundingBlob fn.Option[tlv.Blob]
+
+	// Type is the type of the witness that we are trying to resolve.
+	Type input.WitnessType
+
+	// CloseType is the type of close that we are trying to resolve.
+	CloseType CloseType
+
+	// CommitTx is the force close commitment transaction.
+	CommitTx *wire.MsgTx
+
+	// CommitFee is the fee that was paid for the commitment transaction.
+	CommitFee btcutil.Amount
+
+	// ContractPoint is the outpoint of the contract we're trying to
+	// resolve.
+	ContractPoint wire.OutPoint
+
+	// SignDesc is the sign descriptor for the contract.
+	SignDesc input.SignDescriptor
+
+	// KeyRing is the key ring for the channel.
+	KeyRing *CommitmentKeyRing
+
+	// CsvDelay is the CSV delay for the local output for this commitment.
+	CsvDelay uint32
+
+	// BreachCsvDelay is the CSV delay for the remote output. This is only
+	// set when the CloseType is Breach. This indicates the CSV delay to
+	// use for the remote party's to_local delayed output, that is now
+	// rightfully ours in a breach situation.
+	BreachCsvDelay fn.Option[uint32]
+
+	// CltvDelay is the CLTV delay for the outpoint.
+	CltvDelay fn.Option[uint32]
+}
+
+// AuxContractResolver is an interface that is used to resolve contracts that
+// may need additional outside information to resolve correctly.
+type AuxContractResolver interface {
+	// ResolveContract is called to resolve a contract that needs
+	// additional information to resolve properly. If no extra information
+	// is required, a nil Result error is returned.
+	ResolveContract(ResolutionReq) fn.Result[tlv.Blob]
+}