Add Shared Input support

In interactivetxs, add support for shared inputs, similar to shared outputs.
A shared input is optional, and is used in case of splicing to add
the current funding as an input.

Author: optout21

lightning/src/ln/channel.rs

@@ -2771,7 +2771,8 @@ where
 		};
 		let change_value_opt = calculate_change_output_value(
 			self.funding.is_outbound(), self.dual_funding_context.our_funding_satoshis,
-			&shared_funding_output.script_pubkey, &funding_inputs, &funding_outputs,
+			&funding_inputs, None,
+			&shared_funding_output.script_pubkey, &funding_outputs,
 			self.dual_funding_context.funding_feerate_sat_per_1000_weight,
 			change_script.minimal_non_dust().to_sat(),
 		)?;
@@ -2799,6 +2800,7 @@ where
 			is_initiator: self.funding.is_outbound(),
 			funding_tx_locktime: self.dual_funding_context.funding_tx_locktime,
 			inputs_to_contribute: funding_inputs,
+			shared_funding_input: None,
 			shared_funding_output: SharedOwnedOutput::new(shared_funding_output, self.dual_funding_context.our_funding_satoshis),
 			outputs_to_contribute: funding_outputs,
 		};
@@ -11812,6 +11814,7 @@ where
 				funding_tx_locktime: dual_funding_context.funding_tx_locktime,
 				is_initiator: false,
 				inputs_to_contribute: our_funding_inputs,
+				shared_funding_input: None,
 				shared_funding_output: SharedOwnedOutput::new(shared_funding_output, our_funding_satoshis),
 				outputs_to_contribute: Vec::new(),
 			}

lightning/src/ln/dual_funding_tests.rs

@@ -89,13 +89,14 @@ fn do_test_v2_channel_establishment(session: V2ChannelEstablishmentTestSession)
 	let tx_add_input_msg = TxAddInput {
 		channel_id,
 		serial_id: 2, // Even serial_id from initiator.
-		prevtx: initiator_funding_inputs[0].1.clone(),
+		prevtx: Some(initiator_funding_inputs[0].1.clone()),
 		prevtx_out: 0,
 		sequence: initiator_funding_inputs[0].0.sequence.0,
 		shared_input_txid: None,
 	};
-	let input_value =
-		tx_add_input_msg.prevtx.as_transaction().output[tx_add_input_msg.prevtx_out as usize].value;
+	let input_value = tx_add_input_msg.prevtx.as_ref().unwrap().as_transaction().output
+		[tx_add_input_msg.prevtx_out as usize]
+		.value;
 	assert_eq!(input_value.to_sat(), session.initiator_input_value_satoshis);
 
 	nodes[1].node.handle_tx_add_input(nodes[0].node.get_our_node_id(), &tx_add_input_msg);