lnwallet/chanfunding: add optional tapscript root

lnwallet/chanfunding/canned_assembler.go

@@ -58,6 +58,14 @@ type ShimIntent struct {
 	// generate an aggregate key to use as the taproot-native multi-sig
 	// output.
 	musig2 bool
+
+	// tapscriptRoot is the root of the tapscript tree that will be used to
+	// create the funding output. This field will only be utilized if the
+	// MuSig2 flag above is set to true.
+	//
+	// TODO(roasbeef): fold above into new chan type? sum type like thing,
+	// includes the tapscript root, etc
+	tapscriptRoot fn.Option[chainhash.Hash]
 }
 
 // FundingOutput returns the witness script, and the output that creates the
@@ -79,7 +87,7 @@ func (s *ShimIntent) FundingOutput() ([]byte, *wire.TxOut, error) {
 		// the keys are sorted before use.
 		return input.GenTaprootFundingScript(
 			s.localKey.PubKey, s.remoteKey, int64(totalAmt),
-			fn.None[chainhash.Hash](),
+			s.tapscriptRoot,
 		)
 	}
 

lnwallet/chanfunding/psbt_assembler.go

@@ -534,6 +534,7 @@ func (p *PsbtAssembler) ProvisionChannel(req *Request) (Intent, error) {
 		ShimIntent: ShimIntent{
 			localFundingAmt: p.fundingAmt,
 			musig2:          req.Musig2,
+			tapscriptRoot:   req.TapscriptRoot,
 		},
 		State:         PsbtShimRegistered,
 		BasePsbt:      p.basePsbt,

lnwallet/chanfunding/wallet_assembler.go

@@ -394,7 +394,6 @@ func (w *WalletAssembler) ProvisionChannel(r *Request) (Intent, error) {
 		// we will call the specialized coin selection function for
 		// that.
 		case r.FundUpToMaxAmt != 0 && r.MinFundAmt != 0:
-
 			// We need to ensure that manually selected coins, which
 			// are spent entirely on the channel funding, leave
 			// enough funds in the wallet to cover for a reserve.
@@ -539,6 +538,7 @@ func (w *WalletAssembler) ProvisionChannel(r *Request) (Intent, error) {
 				localFundingAmt:  localContributionAmt,
 				remoteFundingAmt: r.RemoteAmt,
 				musig2:           r.Musig2,
+				tapscriptRoot:    r.TapscriptRoot,
 			},
 			InputCoins: selectedCoins,
 			coinLeaser: w.cfg.CoinLeaser,