tapchannel: use stxo on aux chan closer

For the cooperative channel closing we also need to check if the parties
have agreed upon the usage of stxo proofs. If that is the case, we'll
include those commitments in the coop channel closing transaction &
proof.

Author: GeorgeTsagk

tapcfg/server.go

@@ -660,6 +660,7 @@ func genServerConfig(cfg *Config, cfgLogger btclog.Logger,
 			GroupVerifier:      groupVerifier,
 			ChainBridge:        chainBridge,
 			IgnoreChecker:      ignoreCheckerOpt,
+			AuxChanNegotiator:  auxChanNegotiator,
 		},
 	)
 	auxSweeper := tapchannel.NewAuxSweeper(

tapchannel/aux_closer.go

@@ -15,6 +15,7 @@ import (
 	"github.com/lightninglabs/taproot-assets/fn"
 	"github.com/lightninglabs/taproot-assets/proof"
 	"github.com/lightninglabs/taproot-assets/tapchannelmsg"
+	"github.com/lightninglabs/taproot-assets/tapfeatures"
 	"github.com/lightninglabs/taproot-assets/tapfreighter"
 	"github.com/lightninglabs/taproot-assets/tapgarden"
 	"github.com/lightninglabs/taproot-assets/tappsbt"
@@ -66,6 +67,11 @@ type AuxChanCloserCfg struct {
 	// IgnoreChecker is an optional function that can be used to check if
 	// a proof should be ignored.
 	IgnoreChecker lfn.Option[proof.IgnoreChecker]
+
+	// AuxChanNegotiator is responsible for producing the extra tlv blob
+	// that is encapsulated in the init and reestablish peer messages. This
+	// helps us communicate custom feature bits with our peer.
+	AuxChanNegotiator *tapfeatures.AuxChannelNegotiator
 }
 
 // assetCloseInfo houses the information we need to finalize the close of an
@@ -454,11 +460,21 @@ func (a *AuxChanCloser) AuxCloseOutputs(
 			"packets: %w", err)
 	}
 
+	features := a.cfg.AuxChanNegotiator.GetChannelFeatures(
+		lnwire.NewChanIDFromOutPoint(desc.ChanPoint),
+	)
+	supportSTXO := features.HasFeature(tapfeatures.STXOOptional)
+
+	var opts []tapsend.OutputCommitmentOption
+	if !supportSTXO {
+		opts = append(opts, tapsend.WithNoSTXOProofs())
+	}
+
 	// With the outputs prepared, we can now create the set of output
 	// commitments, then with the output index locations known, we can set
 	// the output indexes in the allocations.
 	outCommitments, err := tapsend.CreateOutputCommitments(
-		vPackets, tapsend.WithNoSTXOProofs(),
+		vPackets, opts...,
 	)
 	if err != nil {
 		return none, fmt.Errorf("unable to create output "+
@@ -733,10 +749,22 @@ func (a *AuxChanCloser) FinalizeClose(desc chancloser.AuxCloseDesc,
 				closeInfo.allocations,
 			)
 
+			features := a.cfg.AuxChanNegotiator.GetChannelFeatures(
+				lnwire.NewChanIDFromOutPoint(desc.ChanPoint),
+			)
+			supportSTXO := features.HasFeature(
+				tapfeatures.STXOOptional,
+			)
+
+			var opts []proof.GenOption
+			if !supportSTXO {
+				opts = append(opts, proof.WithNoSTXOProofs())
+			}
+
 			proofSuffix, err := tapsend.CreateProofSuffixCustom(
 				closeTx, vPkt, closeInfo.outputCommitments,
 				outIdx, closeInfo.vPackets, exclusionCreator,
-				proof.WithNoSTXOProofs(),
+				opts...,
 			)
 			if err != nil {
 				return fmt.Errorf("unable to create proof "+