addpsbtoutput: Add serial_id flag

When set this flag tells addpsbtoutput to add the intiator serial_id to the added output.

Changelog-Changed: addpsbtoutput now allows serial_id to be set while adding which is needed for splicing and dual.

Author: ddustin

wallet/reservation.c

@@ -8,6 +8,7 @@
 #include <common/json_command.h>
 #include <common/json_param.h>
 #include <common/key_derive.h>
+#include <common/psbt_open.h>
 #include <common/type_to_string.h>
 #include <lightningd/chaintopology.h>
 #include <lightningd/channel.h>
@@ -677,13 +678,18 @@ static struct command_result *json_addpsbtoutput(struct command *cmd,
 	struct pubkey pubkey;
 	s64 keyidx;
 	const u8 *b32script;
+	bool *add_initiator_serial_ids;
+	struct wally_psbt_output *output;
+	u64 serial_id;
 
 	if (!param_check(cmd, buffer, params,
 			 p_req("satoshi", param_sat, &amount),
 			 p_opt("initialpsbt", param_psbt, &psbt),
 			 p_opt("locktime", param_number, &locktime),
 			 p_opt("destination", param_bitcoin_address,
 			       &b32script),
+			 p_opt_def("add_initiator_serial_ids", param_bool,
+			 	   &add_initiator_serial_ids, false),
 			 NULL))
 		return command_param_failed();
 
@@ -737,7 +743,13 @@ static struct command_result *json_addpsbtoutput(struct command *cmd,
 	}
 
 	outnum = psbt->num_outputs;
-	psbt_append_output(psbt, b32script, *amount);
+	output = psbt_append_output(psbt, b32script, *amount);
+
+	if (*add_initiator_serial_ids) {
+		serial_id = psbt_new_output_serial(psbt, TX_INITIATOR);
+		psbt_output_set_serial_id(psbt, output, serial_id);
+	}
+
 	/* Add additional weight of output */
 	weight = bitcoin_tx_output_weight(
 			chainparams->is_elements ? BITCOIN_SCRIPTPUBKEY_P2WPKH_LEN : BITCOIN_SCRIPTPUBKEY_P2TR_LEN);