lncli: possibility to define an address type for changes in FundPsbt

With this commit, we can define an address type for default/imported
accounts in FundPsbt using '—change_type' flag. The value for this
flag can only be 'p2tr' at the moment. If not specified, we will use
P2WKH addresses for change outputs. Custom accounts don’t support
this flag as they have a unique scope.

cmd/lncli/walletrpc_active.go

@@ -582,7 +582,7 @@ var fundPsbtCommand = cli.Command{
 	Name:  "fund",
 	Usage: "Fund a Partially Signed Bitcoin Transaction (PSBT).",
 	ArgsUsage: "[--template_psbt=T | [--outputs=O [--inputs=I]]] " +
-		"[--conf_target=C | --sat_per_vbyte=S]",
+		"[--conf_target=C | --sat_per_vbyte=S] [--change_type=A]",
 	Description: `
 	The fund command creates a fully populated PSBT that contains enough
 	inputs to fund the outputs specified in either the PSBT or the
@@ -606,7 +606,14 @@ var fundPsbtCommand = cli.Command{
 	The optional 'inputs' flag decodes a JSON list of UTXO outpoints as
 	returned by the listunspent command for example:
 
-	    --inputs='["<txid1>:<output-index1>","<txid2>:<output-index2>",...]'
+	    --inputs='["<txid1>:<output-index1>","<txid2>:<output-index2>",...]
+
+	The optional '--change-type' flag permits to choose the address type
+	for the change for default accounts and single imported public keys.
+	The custom address type can only be p2tr at the moment (p2wkh will be
+	used by default). No custom address type should be provided for custom
+	accounts as we will always generate the change address using the coin
+	selection key scope.
 	`,
 	Flags: []cli.Flag{
 		cli.StringFlag{
@@ -642,6 +649,17 @@ var fundPsbtCommand = cli.Command{
 			Usage: "(optional) the name of the account to use to " +
 				"create/fund the PSBT",
 		},
+		cli.StringFlag{
+			Name: "change_type",
+			Usage: "(optional) the type of the change address to " +
+				"use to create/fund the PSBT. If no address " +
+				"type is provided, p2wpkh will be used for " +
+				"default accounts and single imported public " +
+				"keys. No custom address type should be " +
+				"provided for custom accounts as we will " +
+				"always use the coin selection key scope to " +
+				"generate the change address",
+		},
 	},
 	Action: actionDecorator(fundPsbt),
 }
@@ -747,6 +765,21 @@ func fundPsbt(ctx *cli.Context) error {
 		}
 	}
 
+	if ctx.IsSet("change_type") {
+		switch addressType := ctx.String("change_type"); addressType {
+		case "p2tr":
+			//nolint:lll
+			req.ChangeType = walletrpc.ChangeAddressType_CHANGE_ADDRESS_TYPE_P2TR
+
+		default:
+			return fmt.Errorf("invalid type for the "+
+				"change type: %s. At the moment, the "+
+				"only address type supported is p2tr "+
+				"(default to p2wkh)",
+				addressType)
+		}
+	}
+
 	walletClient, cleanUp := getWalletClient(ctx)
 	defer cleanUp()