lntest+lnwallet: add ImportTaprootScript to wallet interface

lntest/mock/walletcontroller.go

@@ -132,6 +132,13 @@ func (w *WalletController) ImportPublicKey(*btcec.PublicKey,
 	return nil
 }
 
+// ImportTaprootScript currently returns a dummy value.
+func (w *WalletController) ImportTaprootScript(waddrmgr.KeyScope,
+	*waddrmgr.Tapscript) (waddrmgr.ManagedAddress, error) {
+
+	return nil, nil
+}
+
 // SendOutputs currently returns dummy values.
 func (w *WalletController) SendOutputs([]*wire.TxOut,
 	chainfee.SatPerKWeight, int32, string) (*wire.MsgTx, error) {

lnwallet/interface.go

@@ -316,6 +316,15 @@ type WalletController interface {
 	ImportPublicKey(pubKey *btcec.PublicKey,
 		addrType waddrmgr.AddressType) error
 
+	// ImportTaprootScript imports a user-provided taproot script into the
+	// wallet. The imported script will act as a pay-to-taproot address.
+	//
+	// NOTE: Taproot keys imported through this RPC currently _cannot_ be
+	// used for funding PSBTs. Only tracking the balance and UTXOs is
+	// currently supported.
+	ImportTaprootScript(scope waddrmgr.KeyScope,
+		tapscript *waddrmgr.Tapscript) (waddrmgr.ManagedAddress, error)
+
 	// SendOutputs funds, signs, and broadcasts a Bitcoin transaction paying
 	// out to the specified outputs. In the case the wallet has insufficient
 	// funds, or the outputs are non-standard, an error should be returned.